A subcontractor (P) was not paid progress payments due by Americo (D). P agreed to complete the job after assurances were received from D that payment would be received on completion. A non-waiver of rights and remedies letter was signed by D to allow the subcontractor to bring suit for nonperformance if it were not paid. P completed performance and demanded payment from D. P, in the name of the U.S. under Section 2 of the Miller Act, sued D for payment under the contract and in the alternative for restitution. D moved for a partial summary judgment on the issue of restitution.