Musa has a choice of buying a shirt, a book and a bag. What is the opportunity cost of buying a book?

The opportunity cost of buying a book is the value of the next best alternative that must be given up in order to buy the book. In this case, Musa has a choice of buying a shirt, a book and a bag. Therefore, the opportunity cost of buying a book is the value of the next best alternative foregone by buying the book, which is the alternative with the highest value among the other options. Since the other options are a shirt and a bag, the opportunity cost of buying a book is either a shirt and a bag or a bag only, depending on the value Musa assigns to each option. Therefore, the correct answer is either "A shirit and a bag" or "A bag only".