Calvin wants to start his own business making candles. He can purchase a candle factory that costs $400,000. Calvin currently has $500,000 in the bank earning 3 percent interest per year. Suppose Calvin purchases the factory using $200,000 of his own money and $200,000 borrowed from a bank at an interest rate of 6 percent. What is Calvin's annual opportunity cost of purchasing the factory? $3,000 $123,000 $15,000 $18,000