Suppose you wanted to push this crate up the ramp. The crate's weight is 100 N, and the maximum frictional force the ramp can exert on it is 20 N. To get the crate to start moving up, what's the minimum force you'd have to exert on it: 20 N, 120 N, or some value in-between? Explain, assuming that you're pushing on the lower face of the crate, in a direction parallel to the ramp's surface.