Work, Energy and Power (Variable Friction)

A particle of mass M moves along a horizontal x axis from x = 0 to x = L. The coefficient of kinetic friction varies with x as mu_k(x) = mu_0 - alpha x, where mu_0 and alpha are constants of appropriate dimensions, so that mu_k(L) = 0. The total work done by the frictional force during the motion is n mu_0 MgL, where g is the acceleration due to gravity. The value of n is: