In: Economics
assume a firm has the production function q=k^1/4L^1/4, where k represents capital, L represents labor, r represents the price of capital and w represents the price of labor.
Using the Lagrange method, derive the optimal quantities of k and l as a function of q,r,w
q=k1/4 L1/4
Total cost= wL+rK
Lagrangian function= L''= wL+rK+λ(q-k1/4 L1/4 )
dL''/dK= r-(1/4)λk-3/4 L1/4 = 0
λ = r/(1/4)k-3/4 L1/4 = 4r/k-3/4 L1/4 Equation 1
Put equation 1 and 2 equals to each other:
dL''/dL= w-(1/4)λk1/4 L-3/4 = 0
λ =4w/k1/4 L-3/4 Equation 2
4r/k-3/4 L1/4 = 4w/k1/4 L-3/4
K/L = w/r
K= Lw/r Equation 3
dL''/dλ = q-k1/4 L1/4 =0
k1/4 L1/4 =q
From equation 3:
(Lw/r)1/4 L1/4 =q
L2/4 = q(r/w)1/4
Squaring both sides:
L= q2 (r/w)1/2 Optimal quantity of L
Use L in equation 3:
K= Lw/r = [q2 (r/w)1/2 ] (w/r)= q2 (w/r)1/2 Optimal quantity of K