Suppose that the marginal tax rate is 20%. If a farmer decides to purchase a new tractor, it will increase the operating receipts $6,800 per year but it will cost $1,100 a year for maintenance. Before the purchase, the current operating expenses are $1,200. What is the annual after-tax net return generated by this investment for each year? $4,624 $4,560 $5,100 $5,440