Egbert applies a 20 lb force at the edge of a 4 ft wide door that is half-open in order...

Egbert applies a 20 lb force at the edge of a 4 ft wide door that is half-open in order to close it. (See Figure 1.67.) Assume that the direction of force is perpendicular to the plane of the doorway. What is the torque about the hinge on the door?