Widgeon Co. manufactures three products: Bales, Tales, and Wales. The selling prices are $55, $78, and $32, respectively. The variable costs for each product are $20, $50, and $15, respectively. Each product must go through the same processing in a machine that is limited to 2,000 hours per month. Bales take 5 hours to process; Tales 7 hours; and Wales 1 hour. The contribution per machine hour for Wales is a. $28 b. $7 c. $17 d. $35