C18: A piano mover raises a 100-kg piano at a constant rate using the frictionless pulley system shown here. With how much force is he pulling on the rope? Ignore friction and assume g = 10 m/s².

1. 2,000 N

2. 1,500 N

3. 1,000 N

4. 750 N

5. 500 N

6. 200 N

7. 50 N

8. impossible to determine