Please help me explain each part of the question fully

Joanne is a seventy-five-year-old widow who survives on her husband's small pension.Joanne has become increasingly forgetful, and her family worries that she may have Alzheimer's disease (a brain disorder that seriously affects a person's ability to carry out daily activities). No physician has diagnosed her, however, and no court has ruled on Joanne's legal competence. One day while she is out shopping, Joanne stops by a store that is having a sale on pianos and enters into a fifteen-year installment contract to buy a grand piano. When the piano arrives the next day, Joanne seems confused and repeatedly asks the delivery person why a piano is being delivered. Joanne claims that she does not recall buying a piano. Explain whether this contract is void, voidable, or valid. Can Joanne avoid her contractual obligation to buy the piano? If so, how?