Coefficent of Friction

A 23 kg block rests on a surface which has a coefficient of friction of 0.4.

What will be the value of the inclined force, P, when the block is just on the point of sliding?

P is at 30 degrees upwards from the horizontal

http://gyazo.com/6cd518b1a4d4324182e4d99f1fc50a6c

I need working, I know the answer is ~86.3N, just need full worked solution