A uniform rod of length $200\text{cm}$ and mass $500\text{g}$ is balanced on a wedge placed at $40\text{cm}$ mark. A mass of $2\text{kg}$ is suspended from the rod at $20\text{cm}$ and another unknown mass $m$ is suspended from the rod at $160\text{cm}$ mark. Find the value of $m$ such that the rod is in equilibrium. ($g=10{\text{m/s}}^2$)

1. A
   $1/6\text{kg}$
2. B
   $1/12\text{kg}$
3. C
   $1/2\text{kg}$
4. D
   $1/3\text{kg}$