Thomas Jones' neighbor, Marcus owes him $500 which he borrowed from Thomas two weeks ago and promised he will pay him back on Saturday, April 1st. Thomas owed his sister, Mary $500 which he borrowed from her a month ago. When Marcus borrowed the $500 from Thomas he promised Thomas in an agreement he signed that he would pay the $500 to Mary on April 1st. Marcus has not done so, in other words, he has not paid the $500 to Mary as he promised. Does Mary have any rights? Could she sue to enforce the contract between her brother Thomas and Marcus? What type of beneficiary if any, is Mary