A 40-N Crate Rests on a Rough Horizontal Floor $\mu$ _s = 0

Multiple Choice

A 40-N crate rests on a rough horizontal floor. A 12-N horizonatl force is then applied to it. If the coefficients of friction are $\mu$ _s = 0.5 and $\mu$ _k = 0.4, the magnitude of the frictional force on the crate is:

A) 8 N
B) 12 N
C) 16 N
D) 20 N
E) 40 Nb