# Microeconomics Theory - Production and Cost Function

A firm has the following production function Q and cost function as follows:

**Q= KL** where Q = quantity, K=capital, L=labor

**C= 3L +12K** where C= cost

Calculate the cost when the firm produced 36 units.

Hint: In equilibrium, \(\boxed{MPK/r=MPL/w}\) where MPK and MPL are marginal products of capital and labor respectively; and *w* and *r* are cost of capital and labor.