The 100-lb box shown is being pulled up the inclined surface by the winch. The coefficient of kinetic friction between the box and the surface is μ_k=0.4. The mass moment of inertia of the drum on which the cable is wound, including the cable wound on the drum, is I_A=3 slug∙ft^2. If the motor exerts a torque M=40 ft∙lb on the drum, what is the acceleration of the box?