In: Economics
a) Q = L3 * K4 - L2
MRTS(L,K) = MPL/MPK
MPL: Marginal product of labor
MPK: Marginal product of capital
MPL = dQ/dL
MPL = 3L2 * K4 - 2L
MPK = dQ/dK
MPK = 4K3 * L3
MRTS(L,K) = (3L2 * K4 - 2L)/(4K3 * L3)
MRTS(L,K) = 0.75*K/L - 0.5/(K3*L2)
b) The production function has an uneconomic region where MPL or MPK are negative
MPL < 0
3L2 * K4 - 2L < 0
3L2 * K4 < 2L
3L * K4 < 2
L < 2/(3K4)