13G Filing: Soros Fund Management and Servicesource International Inc. (SREV)

EXHIBIT C

POWER OF ATTORNEY

KNOW
ALL MEN BY THESE PRESENT, that I, ROBERT SOROS, hereby make, constitute and appoint each of MARYANN CANFIELD, JODYE ANZALOTTA, JAY SCHOENFARBER, THOMAS OGRADY and REGAN ONEILL, acting individually, as my agent and attorney-in-fact for the purpose of executing in my name, (a) in my personal capacity or (b) in my capacity as Deputy Chairman of, member of or in other capacities
with Soros Fund Management LLC (SFM LLC) and each of its affiliates or entities advised by me or SFM LLC, all documents, certificates, instruments, statements, filings and agreements (documents) to be filed with or delivered
to any foreign or domestic governmental or regulatory body or required or requested by any other person or entity pursuant to any legal or regulatory requirement relating to the acquisition, ownership, management or disposition of securities,
futures contracts or other investments, and any other documents relating or ancillary thereto, including without limitation all documents relating to filings with the Commodities Futures Trading Commission and National Futures Association, the
United States Securities and Exchange Commission (the SEC) pursuant to the Securities Act of 1933 or the Securities Exchange Act of 1934 (the Act) and the rules and regulations promulgated thereunder, including all documents
relating to the beneficial ownership of securities required to be filed with the SEC pursuant to Section 13(d) or Section 16(a) of the Act and any information statements on Form 13F required to be filed with the SEC pursuant to
Section 13(f) of the Act.

All past acts of these
attorneys-in-fact in furtherance of the foregoing are hereby ratified and confirmed.

Execution of this power of attorney revokes that certain Power of Attorney dated as of the 3rd day of October, 2007 with respect to the same
matters addressed above.

This power of attorney shall be valid from the date hereof until revoked by me.

IN WITNESS WHEREOF, I have executed this instrument as of the 30th day of November, 2015.