You have a part-time job at the library that pays $10 per hour, 4 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 the gas, motel, lift tickets, and other expenses to be around $50. What is your total economic cost of taking the ski trip?
a) $130
b) $60
c) $50
d) $80