A metre rule of uniform density is supported on a pivot at the $34.0\,\text{cm}$ mark, as shown. The rule is in equilibrium when a mass of $64\,\text{g}$ is suspended from the $4.0\,\text{cm}$ mark. What is the mass of the metre rule?
- A$38\,\text{g}$
- B$44\,\text{g}$
- C$120\,\text{g}$
- D$136\,\text{g}$