A Bakelite beaker has volume capacity of 500 cc at 30°C . When it is partially filled with V_m volume (at 30^oC ) of mercury, it is found that the unfilled volume of the beaker remains constant as the temperature is varied. If ${\mathrm{\gamma }}_{(\text{beaker) }}=6\times {{10}^{-6}}^{\circ }{\mathrm{C}}^{-1}$ and ${\mathrm{\gamma }}_{\left(\text{mercury }\right)}=1.5\times {{10}^{-4}}^{\circ }{\mathrm{C}}^{-1}$ where $\mathrm{\gamma }$ is the coefficient of volume expansion, then V_m  (in cc) is close to