9.3 A student pushes a 200-N box of books across the floor. The coefficient of kinetic friction between the carpet and the box is $\mu_k = 0.15$.
(a) If he exerts the force $F$ at angle $\alpha = 25^\circ$, what is the magnitude of the force he must exert to slide the box across the floor?
(b) If he bends his knees more and exerts the force $F$ at angle $\alpha = 10^\circ$, what is the magnitude of the force he must exert to slide the box?
