POWER OF ATTORNEY
               FOR EXECUTING FORM ID, FORM 3, FORM 4 AND FORM 5,
                       FORM 144 AND SCHEDULE 13D AND 13G


       The undersigned hereby constitutes and appoints Justin P. Byrne, Kathy
Raines, and Scott Pittman with full power of substitution, as the undersigned's
true and lawful attorney-in-fact to:

    1. Prepare, execute in the undersigned's name and on the undersigned's
       behalf, and submit to the U.S. Securities and Exchange Commission (the
       "SEC") a Form ID, including amendments thereto, and any other documents
       necessary or appropriate to obtain codes and passwords enabling the
       undersigned to make electronic filings with the SEC of reports required
       by Section 16(a) of the Securities Exchange Act of 1934 or any rule or
       regulation of the SEC;

    2. Execute for and on behalf of the undersigned (a) any Form 3, Form 4 and
       Form 5 (including amendments thereto) in accordance with Section 16(a) of
       the Securities Exchange Act of 1934, as amended (the "Exchange Act"), (b)
       Form 144, (c) Schedule 13D and Schedule 13G (including amendments
       thereto) in accordance with Sections 13(d) and 13(g) of the Exchange Act,
       and (d) any joint filing agreement in connection with the preceding
       clauses (a)-(c);

    3. Do and perform any and all acts for and on behalf of the undersigned that
       may be necessary or desirable to complete and execute any Form ID, Form
       3, Form 4, Form 5, Form 144, Schedule 13D or Schedule 13G (including
       amendments thereto) and timely file the forms or schedules with the SEC
       and any stock exchange or quotation system, self-regulatory association
       or any other authority, and provide a copy as required by law or
       advisable to such persons as the attorney-in-fact deems appropriate; and

    4. Take any other action in connection with the foregoing that, in the
       opinion of the attorney-in-fact, may be of benefit to, in the best
       interest of or legally required of the undersigned, it being understood
       that the documents executed by the attorney-in-fact on behalf of the
       undersigned pursuant to this Power of Attorney shall be in the form and
       shall contain the terms and conditions as the attorney-in-fact may
       approve in the attorney-in-fact's discretion.

       The undersigned hereby grants to the attorney-in-fact full power and
authority to do and perform all and every act requisite, necessary or proper to
be done in the exercise of any of the rights and powers herein granted, as fully
to all intents and purposes as the undersigned might or could do if personally
present, with full power of substitution or revocation, hereby ratifying and
confirming all that the attorney-in-fact shall lawfully do or cause to be done
by virtue of this Power of Attorney and the rights and powers granted herein.

       This Power of Attorney shall remain in full force and effect until the
undersigned revokes this Power of Attorney in a signed writing delivered to the
attorney-in-fact.  This Power of Attorney does not revoke any other power of
attorney that the undersigned has previously granted.

       IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to
be executed as of this 20th day of December, 2019

                                   Name:  Mark McFarland

                                   Title: Director

                                   Signature:   /s/ Mark McFarland
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