At the beginning of the year, Hank puts $100,000 into an investment. At the end of the year, the investment is completed and he is given a check for $110,000. Meanwhile, Susan puts $100,000 in another investment, and receives $140,000.
In retrospect, what was Hank's opportunity cost?
a. $30,000 b. $40,000 c. $100,000 d. $110,000