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