An object of mass 50kg rests on a rough plane incline at an angle alpha to the horizontal. It is supported in this position by a light string parallel to the plane. The string has a breaking strain of 200N and the coefficient of friction between the object and the plane is 0.2. Find the largest value of alpha for the string to remain intact.

Resolving parallel to the plane:

50gsin(alp) = 200 + (0.2x50gcos(alp))

= 200 + 10gcos(alp)

From here I don't know what to do.

Any help would be much appreciated. Thanks :)