A firm estimates its production function as Q = XXXXXXXXXX*L -.5*L 2 + 30*K -1.00*K 2 + 15*F -.3*F 2 . Total cost is TC = $2*L + $2.5*K + $1.75*F. The firm wishes to produce 400 units of output. Use...

A firm estimates its production function as

Q = -2.4 + 20*L -.5*L²
+ 30*K -1.00*K²
+ 15*F -.3*F². Total cost is TC = $2*L + $2.5*K + $1.75*F.  The firm wishes to produce 400 units of output.  Use Excel to find the cost minimizing amounts of L, K and F. How much F (Fuel) should the firm use?