Sharon has just paid down on a small apartment for which the mortgage is 2,200 per month. Before she moves in, a work colleague offers to rent it for 5,000 per month. Since Sharon is longing to move out of her parents house even though she doesn't have to pay rent there, she declines the rental offer and occupies her new apartment. What is the value of the opportunity cost of her choice?
1) 2,800
2) 2,200
3) 5,000
4) 7,200
5) zero