An unknown mass and a $1.00\,\text{kg}$ mass are attached to the two opposite ends of a bar. The bar has negligible mass and a total length of $30.0\,\text{cm}$. The bar is in equilibrium when it is supported by a pivot located $20.0\,\text{cm}$ from the unknown mass, as shown. Determine the unknown mass.
- A$333\,\text{g}$
- B$500\,\text{g}$
- C$667\,\text{g}$
- D$1000\,\text{g}$