Exhibit 4

JOINT FILING AGREEMENT

Pursuant to and in accordance with the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and the rules and regulations thereunder, each party agrees to the joint filing, on behalf of each of them, of any filing required by such party under Section 13 or Section 16 of the Exchange Act of any rule or regulation thereunder (including any amendment, restatement, supplement and/or exhibit thereto) with the Securities and Exchange Commission (and, if such security is registered on a national securities exchange, also with the exchange), and further agrees to the filing, furnishing and/or incorporation by reference of this agreement as an exhibit thereto. The agreement shall remain in full force and effect until revoked by either party hereto in a signed writing provided to each other party hereto, and then only with respect to such revoking party.

IN WITNESS WHEREOF, each party hereto, being duly authorized, has caused this agreement to be executed and effective as of the date written below.

Dated: January 3, 2019

John C. Goff
By:	/s/ John C. Goff
Goff REN Holdings, LLC  By: its Manager, GFS REN GP, LLC
By:	/s/ John C. Goff
	John C. Goff, Chief Executive Officer
Goff MCEP Holdings, LLC
By: its Manager, Goff Capital, Inc.
By:	/s/ John C. Goff
	John C. Goff, President
Goff MCEP II, LP
By: its General Partner, GFS MCEP GP, LLC
By:	/s/ John C. Goff
	John C. Goff, Chief Executive Officer
Goff Focused Energy Strategies, LP
By: its General Partner, GFS Energy GP, LLC
By:	/s/ John C. Goff
	John C. Goff, Chief Executive Officer
GFS Management, LLC
By: its managing member, Goff Focused Strategies, LLC
By:	/s/ John C. Goff
	John C. Goff, Chief Executive Officer
Goff Focused Strategies, LLC
By:	/s/ John C. Goff
	John C. Goff, Chief Executive Officer
Goff Family Investments, LP
By: its General Partner, Goff Capital, Inc.
By:	/s/ John C. Goff
	John C. Goff, President

Goff Capital, Inc.
By:	/s/ John C. Goff
	John C. Goff, President
GFS REN GP, LLC
By: its Managing Member, GFS Management, LLC
By: its Managing Member, Goff Focused Strategies, LLC
By:	/s/ John C. Goff
	John C. Goff, Chief Executive Officer
GFS MCEP GP, LLC
By: its Managing Member, GFS Management, LLC
By: its Managing Member, Goff Focused Strategies, LLC
By:	/s/ John C. Goff
	John C. Goff, Chief Executive Officer
GFS Energy GP, LLC
By: its Managing Member, GFS Management, LLC
By: its Managing Member, Goff Focused Strategies, LLC
By:	/s/ John C. Goff
	John C. Goff, Chief Executive Officer
GFT Strategies, LLC
By: its controlling equity holder, John C. Goff 2010 Family Trust
By:	/s/ John C. Goff
	John C. Goff, Trustee
John C. Goff 2010 Family Trust
By:	/s/ John C. Goff
	John C. Goff, Trustee