The drawing shows three blocks, each with the same mass, stacked one upon the other. The bottom block rests on a frictionless horizontal surface and is being pulled by a force F(vector) that is parallel to this surface. The surfaces where the blocks touch each other have identical coefficients of static friction. Which one of the following correctly describes the magnitude of the net force of static friction f_s that acts on each block?

(a) f_s,A = f_s,B = f_s,C

(b) f_s,A = f_s,B = ½ f_s,c

(c) f_s,A = 0 and f_s,B = ½ f_s,C

(d) f_s,c = 0 and f_s,A = ½ f_s,B

(e) f_s,A = f_s,C = ½ f_s,B

A B