Lagrange multiplier problem

Hello I'm stuck on this problem.

P(L,K) = 100L^0.25 * K^0.75

P = production output

L = labour

K = capital

Suppose that labour costs $40 per unit and capital costs are $60 per unit. Units lagrange multipliers, find the least expensive way of producing 10 000 units of output

This is what i've done so far.

C(L,K) = 40L + 60K P(L,K) = 100L^0.25 x K^0.75 = 10 000

**∆**C = λ**∆**P

**∆**C = 40i + 60j ** ∆**P = 25λ(K/L)^0.75 i + 75λ(L/K)^0.25 j

40 = 25λ(K/L)^0.75 60 = 75λ(L/K)^0.25

2(L/K)^0.25 = (L/K)^0.75

2L = K

P(L,2L) = 100L^0.25 x 2L^0.75 = 10 000

10 000 = 200L

L = 50

C(L,2L) = 40(50) + 60(100) = 8000

The examples I did in class were much different, they had values +/- for x, and you just use the - for the min.

I'm lost, I'm not sure if this is a min or a max.

Anyhelp will be greatful. =)