The midpoint of a uniform metre rule is supported on a pivot. A load with weight $3.0\,\text{N}$ is positioned at the $70\,\text{cm}$ mark. An upward force $F$ is applied at the $80\,\text{cm}$ mark. The rule is in equilibrium. What is the magnitude of $F$?
- A$2.0\,\text{N}$
- B$2.6\,\text{N}$
- C$3.0\,\text{N}$
- D$4.5\,\text{N}$