During the time Mary spent studying macroeconomics, she could have instead either made brownies or played the piano. She thinks to herself that if she wasn't studying, then she would have made brownies. In this case, her opportunity cost of studying is equal to which of the following? The amount of time Mary spent studying. The value of playing the piano. The value of making brownies, which is her next best alternative. The cost of the ingredients needed to make brownies