In the diagram, a uniform solid rectangular block has weight $50\,\text{N}$ and is pivoted at point $P$. Its height is $40\,\text{cm}$, while its base measures $8.0\,\text{cm}$ across. Which horizontal force $F$ is just sufficient to cause the block to begin turning about $P$?
- A$2.5\,\text{N}$
- B$5.0\,\text{N}$
- C$10\,\text{N}$
- D$160\,\text{N}$