Let a firm use labor (L) and capital (K) as its only inputs to produce an output, Q. The cost of labor is w = $3 per labor hour and the cost of capital is r = $12 per machine hour. What is the equation of the $180 isocost line? A. 3L +12 K = 60 O B. 12L + 3K = 180 O C. L+4K = 60 D. K = (180/3) + (12/3) L E. K = 60 - 3L