17) answer the question on the basis of the following output data for a firm. assume that the amounts of all nonlabor resources are fixed. number of workers units of output 0 0 1 35 2 80 3 135 4 170 5 195 6 215 average product is at a maximum when a) three worker(s) is/are hired. b) four worker(s) is/are hired. c) two worker(s) is/are hired. d) six worker(s) is/are hired