farmer ling grows rice. if he plants 0 seeds, then there is no harvest. if he plants 1 bushel of seeds, then he gets 50 pounds of rice. if he plants 2 bushels of seeds, he gets 90 pounds of rice. if he plants 3 bushels of seeds, he gets 120 pounds of rice. if a bushel of seeds costs $100 each and this is the only cost, the total-cost curve is