A 50 kg uniform ladder, 5.0 m long, is placed against a smooth wall at a height of h = 3.7 m. The base of the ladder rests on a rough horizontal surface whose coefficient of static friction is 0.40. An 80 kg block is suspended from the top rung of the ladder, just at the wall. In Figure 10.12, the magnitude of the force exerted on the base of the ladder, due to contact with the rough horizontal surface is closest to: