When a body of mass $8\,\text{kg}$ is attached to a spring balance, the reading of the balance is $20\,\text{cm}$. Instead of $8\,\text{kg}$, if another body of mass $M$ is suspended from the spring balance and is made to oscillate vertically, the time period of oscillation is $\pi/5\,\text{s}$, then the value of $M$ is (Acceleration due to gravity $= 10\,\text{ms}^{-2}$)