All amounts due under this Section shall be payable not later than 30 days after demand therefor, provided , however, that any Indemnitee that has received any indemnification payment pursuant to the express provisions of clause (b)  preceding, shall promptly refund such payment to the extent that there is a final and nonappealable judgment of a court of competent jurisdiction that such Indemnitee was not entitled to such indemnification payment pursuant to the express provisions of clause (b)  preceding.