James contracts to make repairs to Bettys building in return for Bettys promise to pay $12,000 on completion of the repairs. After partially completing the repairs, James is unable to continue. Betty refuses to pay James and hires another builder, who completes the repairs for $5,000. The buildings value to Betty has increased by $10,000 as a result of the repairs by James, but Betty has lost $500 in rents because of the delay caused by Jamess breach. James sues Betty. How much, if any, may James recover in restitution from Betty