Adam, Bob, Carol and Diane need a kidney transplant. Each of them has a family member who is willing to donate one, but not all kidneys are the same. Adam's sister's kidney is adequate for Adam, Bob and Carol. Bob's brother's kidney only works for Diane. Carol's mother's kidney is good for Diane and Adam. Diane's sister's kidney is adequate for Bob and Carol. Assume that each of them only cares about getting a transplant. (a) Find the allocations that are Pareto Optimal. (b) Find the final allocation induced by the top trading cycles mechanism. (c) Suppose that each individual would rather have a kidney from their own family as no kidney and they are given the right to block it. Is the resulting allocation from top trading cycles efficient? Discuss.