A uniform beam is supported on a pivot at its midpoint. Two weights are fixed to the beam at the positions shown, and an upward force $F$ keeps the beam balanced. What is the size of $F$?
- A$6.0\,\text{N}$
- B$12\,\text{N}$
- C$30\,\text{N}$
- D$60\,\text{N}$