C26: A 1-kg rock is suspended by a massless string from one end of a 1-m measuring stick. What is the weight of the measuring stick if it is balanced by a support force at the 0.25-m mark?

1. 0.25 kg

2. 0.5 kg

3. 1 kg

4. 2 kg

5. 4 kg

6. impossible to determine