#1PROJECT BRONCO CONFIDENTIAL DISCUSSION MATERIALS September 17, 2018 E Confidential - Preliminary Draft BAIRD#2SUMMARY OF CITI CONSTRUCT FOR BRIDGING THE AM COMMITTEE "GAP" ■ minary Praft - AMGP has offered an exchange ratio of 1.775x, including $3.00 in cash AR has signaled that this is acceptable AM Committee is holding out for an all-in 1.850x exchange ratio AMGP offered AM unaffiliated public unitholders $0.415/unit special dividend in cash which helps to bridge the bid/ask gap, however AM has held firm at a 1.850x exchange ratio Warburg has hired Citigroup to see if they can develop a solution to break the AM/AMGP impasse Citi called Baird to suggest that the "value gap" between AR and AM LPs is 4.5 million shares based on the difference between a 1.775x exchange rate plus the $0.415/unit special distribution and the 1.850x exchange rate which AM LP Committee wants (we will discuss the correct gap in the following pages) Citi is proposing that all four parties to the negotiations split the 4.5 million share gap as set forth below: AR: the number of shares at the 1.775x exchange ratio would be reduced by 1.125 million (<1%). Those shares would be given to AM's unaffiliated public unitholders. AR would also get a $0.415/unit special dividend ($41.5 million) which would more than offset the current value of the 1.125 million units we are being asked to contribute to AM's public unitholders AMGP would issue an additional 1.125 million shares to the AM public unitholders. Note; this is a cost shared by all of the pro-forma shareholders, not just the existing AMGP holders. An alternative discussed with Citi is to have the existing AMGP holders bear the full cost associated with the 1.125 million shares (we would adjust ratios to achieve this) Series B would give up 1.125 million shares and get 17.375 million shares instead of 18.5 million AM public unitholders would get $0.415 per unit in cash (via the special dividend) and an additional 3.375 million units above a 1.775x exchange ratio (which would leave them 1.125 million shares under the 1.850x exchange ratio demand) BAIRD Project Bronco Page 2#3SUMMARY OF CITI CONSTRUCT FOR BRIDGING THE AM COMMITTEE "GAP" ...continued minans Draft Baird will review the economics associated with the Citi construct on the following pages ***** Citi is discussing this Construct with TPH and Goldman, and assuming agreement is reached among the Committees, Peter Kagan will present the solution to Paul and Glen and press them to contribute their share to the solution. BAIRD Project Bronco Page 3#4CURRENT AM / AMGP BID-ASK GAP ($ and shares in millions) Consideration to ALL AM Holders, including AM Units Held by AR 1.607x Equity Component 0.168x $3.00/unit cash converted to exchange ratio equivalent based on AMGP 20-day VWAP Cash Component 1.775x Source: Bloomberg market data as of September 14, 2018. Total Merger Consideration Additional Public AM Consideration 0.023x $0.415/unit cash converted to exchange ratio equivalent based on AMGP 20-day VWAP Special Dividend to Midstream Public (a) Current all-in exchange ratio to AM (b) AM desired all-in exchange ratio (c) Gap in exchange ratio (d) Number of unaffiliated AM units (e) Implied share gap (c* d) (f) Current AMGP share price (g) Total value gap AM "All-in" Exchange Ratio 1.798x Exchange Ratio to Midstream Public 1.798x 1.850x 0.052x 88.2 4.57 $17.22 $78.7 Preliminary Prart Remaining Bid/Ask Gap 0.052x Gap in Bid-Ask AM Ask 1.850x AM Ask BAIRD Note, for discussion purposes, we will utilize 4.5 mm shares as the "gap", given recent discussions have centered on this number Project Bronco Page 4#5PROPOSED "SPLIT THE DIFFERENCE" CONSTRUCT ($ and shares in millions) SHARE IMPACT VS. CURRENT PROPOSAL Shares "Added" Shares "Given Up" Total Share Impact Current AMGP Share Price Share Value Impact Special Dividend Inclusion ($0.415) Total Impact Source: Bloomberg market data as of September 14, 2018. AR (1.125) (1.125) $17.22 ($19.4) $41.5 $22.1 AMGP 1.125 (1.125) $17.22 Series B (1.125) (1.125) $17.22 ($19.4) ($19.4) Prelimina a Graft AM 3.375 3.375 $17.22 $58.1 previously included $58.1 $77.5 BAIRD vs. "4.5 mm share Value Gap" ($19.4) Implied AM "Give Up' Project Bronco Page 5#6....... REVISED COMPONENTS OF TOTAL CONSIDERATION ($ in millions) AR AM 1.607x Equity Component 1.607x Equity Component Original Proposal 0.168x Cash Component 0.168x Cash Component Source: Bloomberg market data as of September 14, 2018. (1) Based on 20-day AMGP VWAP ended September 14, 2018. 1.775x Total Merger Consideration Original Proposal 1.775x Total Merger Consideration Impacts of "Split" Construct 0.023x AR's inclusion in special dividend Special Dividend 0.023x Special Dividend 1.798x All-in Exchange Ratio 1.798x All-in Exchange Ratio Preliminary Grafi 0.011x 1.125 mm share reduction Impact of "Split" Construct 0.038x 3.375 mm share increase ****** BAIRD All-In Exchange Ratio 1.787x Revised Total Exchange Ratio All-In Exchange Ratio 1.836x Revised Total Exchange Ratio Project Bronco Page 6#7PRO FORMA IMPACT ($ in millions, unless otherwise noted) Dividend per AR-Owned AM Unit Accretion / (Dilution) ($0.11) (3.8%) $5.00 $4.00 $3.00 $2.00 $1.00 $0.00 $3.00 $2.00 $1.00 ($0.00) 0.0% $0.00 Excludes cash received at close $2.21 $2.21 2019E 2020E Dividend per AMGP Share 1.31x 1.18x $0.50 55.9% $0.89 $2.85 $2.74 $1.38 1.16x 1.16x $0.38 28.2% ($0.02) (0.7%) $1.34 $3.42 $3.40 1.11x 1.11x Accretion/(Dilution) 2021E $0.38 22.1% $1.72 $1.74 $2.13 Status Quo $0.06 1.5% $4.10 $4.16 1.05x 1.05x 2022E $0.39 17.4% $2.22 $2.61 Pro Forma Dividend per Public AM Unit $5.00 $4.00 $3.00 $2.00 $1.00 $0.00 Couliezvish Preliminary Draft $50 $40 $30 $20 $10 $0 $0.07 3.1% Excludes cash received at close $2.21 $2.28 2019E Cash Flow to Series B $12 ($12) (100%) Dividend Holiday ↓ $0 Accretion/(Dilution) $2.85 $2.83 ($0.02) (0.8%) $19 2020E $30 $0.08 2.4% $3.42 $3.50 2021E Accretion /(Dilution) $11 55% $26 $11 44% $37 2019E 2020E 2021E 2022E 2019E 2020E 2021E Assumes AMGP purchases 100% of AM public units (188.1 million on a fully diluted basis) with a combination of equity and $3.41 cash per AM LP unit; AMGP issues 304.6 million shares to current AM unitholders (see page 5). Ako assumes that AMGP issues 17.375 million shares in exchange for 100% of the Series B units. Further, the 2019 pro forma dividend such that dividends to AR-owned AM units are held flat; and Series B unitholders forgo dividends in 2019. $4.10 $33 BAIRD $0.19 4.7% 2022E Project Bronco $4.29 $12 37% $45 2022E Page 7#8SUMMARY RESPONSE TERMS TO CITI PROPOSAL Conditions for AR Committee Support of the CITI Economics Plan: 1) 4.5 million share gap is subject to AR getting $0.415/unit special cash dividend Preliminara. Praft 3) Series B agrees to reduce shares by 1.125 million 2) Economic ratios adjusted to have existing AMGP holders forego the economics on 1.125 million shares 4) AR pro forma distributions held flat for first four quarters 5) Is AR willing to take more than $3.00 per unit in cash if AM public LPs elect to take all equity in the exchange? BAIRD Project Bronco Page 8#9DETAILED COMPARISON OF CONSIDERATION ISSUED ($ and shares in millions) Equity Component Cash Components Total Exchange Ratio Equity Consideration Pre-"Split" Construct Equity Exchange Ratio (¹) AM Units Receiving Merger Consideration New AMGP Shares Issued Impact of "Split the Difference" Construct Total Shares Issued Revised Equity Exchange Ratio Merger Cash Consideration Cash / AM Unit AM Units Receiving Merger Consideration Merger Consideration Cash Cash Consideration Equivalent Exchange Ratio Special Cash Dividend Special Dividend / AM Unit Units Receiving Special Dividend Total Special Dividend Special Dividend Equivalent Exchange Ratio Total Cash Consideration ALL IN EXCHANGE RATIO AR 1.607x 99.943 160.645 (1.125) 159.520 1.596x AR 3.000 99.943 $299.8 0.168x AR $0.415 99.943 $41.5 0.023x (20 $341.3 (2) ▬▬▬▬▬▬▬▬▬▬▬ AR 1.787x AM 1.607x 88.164 141.711 3.375 145.086 1.646x AM 3.000 88.164 $264.5 0.168x AM $0.415 88.164 $36.6 0.023x $301.1 Commande Freliminar Drafti AM 1.836x Series B 18.500 Source: Bloomberg market data as of September 14, 2018, (1) Based on 20-day AMGP VWAP ended September 14, 2018. (2) Includes approximately 1.1 mm AM units issued via the LTIP program at AM; assumed to carry same treatment as AR-held units. To be confirmed. (1.125) 17.375 Series B $0.0 Series B $0.0 Total Shares 188.1 320.856 1.125 321.981 Total Cash $564.3 $78.1 $642.4 Existing AMGP Shares 186.200 186.200 BAIRD Total "AMC" Shares Project Bronco 507.056 1.125 508.181 Page 9