Maria can read 20-pages of economics in an hour. She can also read 50-pages of sociology in an hour. She spends 5 hours per day studying. What is Maria's opportunity cost of reading 100-pages of sociology?

You win $100 in a basketball pool. You have a choice between spending the money now or putting it away for a year in a bank account that pays 5 percent interest. What is the opportunity cost of spending that $100 now? (No need to give an exact calculation.)