Economics differentiation question

Can somebody walk me through this answer

I have these:

$\displaystyle w = ∂F(K, AL) / ∂L$ and $\displaystyle r = ∂F(K, AL) / ∂K$.

Where $\displaystyle K = K/AL$

I have the answer $\displaystyle A[ f (k) - kf '(k)]$ but confused on the steps to prove it

Thanks

Re: Economics differentiation question

define all terms and tell us what the question wants you to do first !

Re: Economics differentiation question

$\displaystyle A = Technology$

$\displaystyle l = Labour$

$\displaystyle K = Capital$

$\displaystyle w = Marginal product of labour$

$\displaystyle R = Marginal product of capital$

I've got to show the MPL is the function provided above (the answer)