Note: Fig
The figure above shows the forces exerted on a block that is sliding on a rough horizontal surface: The weight of the block is 500 N, the normal force is 500 N, the frictional force is 100 N, and there is an unknown force F exerted to the right. The acceleration of the block is .4m/s^2. The value of F is most nearly
A) 20 N
B) 80 N
C) 110 N
D) 120 N
