You have a part-time work-study job at the library that pays $10 per hour, 3 hours per day on Saturdays and Sundays. Some friends want you to join them on a weekend ski trip leaving Friday night and returning Monday morning. They estimate your share of gas, motel, lift tickets, and other expenses to be around $30. Question: What is your total cost for the trip? Consider - and list - both explicit and implicit costs.