First, suppose that Charlie owes Alice $100. Charlie is on his way to pay Alice the money when it falls out of his pocket. It is picked up by Bob. Charlie does not now have enough money to pay Alice. Does Alice have a claim based on unjust enrichment against Bob in respect to the $100? Secondly, suppose that Alice has an account with Megabank. Megabank pays $100 to Bob, mistakenly believing that Alice has instructed it to do so, and debits Alice's account accordingly. Megabank goes into liquidation. Does Alice have a claim against Bob to recover the $100? Thirdly, suppose that Alice sells a painting to Charlie very cheaply, mistakenly believing Charlie to be her brother. Charlie knows that Alice has made a mistake and that he will soon be asked to return the painting. In an attempt to make a profit, he sells the painting on to Bob. The sale is at a low price because Bob knows that the painting does not really belong to Charlie. Can Alice recover the painting or its value from Bob in an action based on unjust enrichment?