A toy manufacturer produces its toys according to the production function:

Q = 5K + 4L

where

Q = output of toys per hour

K = capital input per hour

L = labor input per hour

a) If K = 40, how much L is needed to produce 300 toys per hour?

b) If L = 50, how much K is needed to produce 500 toys per hour?

c) Does this function exhibit constant return to scale, increasing return to scale or decreasing return to scale. Prove your answer.