Ben Says He Will Sell Catalina a Ring That He

Ben says he will sell Catalina a ring that he found in his yard. Ben and Catalina look at the ring and decide that they are not sure what it is, probably just a shiny stone. Catalina pays Ben $10 for the ring. The ring turns out to be a diamond worth much more than $10. Ben wants the ring back, and Catalina refuses. What is the most likely result?

A) The ring will be returned to Ben because of mutual mistake.
B) The ring will be returned to Ben because of unilateral mistake.
C) The ring will be returned to Ben because of equity.
D) The ring will remain with Catalina unless Ben can establish that he was negligent in not recognizing the ring's true value.
E) The ring will remain with Catalina because the parties contracted on the assumption that they did not know the value of the ring.