The coefficients of friction between the block and the rail are µs, = 0.30 and µk = 0.25....

The coefficients of friction between the block and the rail are µs, = 0.30 and µk = 0.25. Knowing that θ = 65°, determine the smallest value of P required (a) to start the block moving up the rail, (b) to keep it from moving down.