Use given data to find level of L,K where profit is maximum?

Q=K^a L^b        cobb douglas production function

a+b=1 , a=b      elasticity is same and equal to1

P=P'                  Constant price because of perfect competition

C=wL+rK           Cost Function

R=Q*P               Revenue function

PI=R-C              Profit function

use given data to find level of L,K where profit is maximum?