Answer:
Opportunity Cost = Batman Shirt
Step-by-step explanation:
Opportunity Cost is the coat of next best alternative forgone while making a choice.
Eg: Working as a teacher with salary Rs 20000, if a teacher sacrifises private coaching income = Rs 15000. Latter (Rs 15000) is the next best alternative forgone while choosing school teaching.
Similarly, Bill choosing Superman T-shirt has opportunity cost as value of his second best choice foregone i.e Batman T-shirt