A glass flask of volume $200 \; cm^3$ is completely filled with mercury at $20^{\circ}C$. The amount of mercury that spilt over when the flask is heated to $80^{\circ}C$ is (coefficient of volume expansion for glass $27 \times 10^{-8} /^{\circ}C$, mercury $0.18 \times 10^{-8}/^{\circ}C$) :
