1. In 2010, Alice paid $20,000 for an option to purchase ten acres of land. By paying the $20,000, she bought the right to buy the land for $100,000 in 2020. When she acquired the option in 2010, the land was worth $120,000. In 2020, it is worth $110,000. What is her opportunity cost of letting the option expire? And what is her sunk cost?