Mean life of a radioactive substance is 1620 and 2160 years for $\alpha$ and $\beta$ emission respectively. At any instant $\alpha$ particles are emitted at a rate of $4\times {10}^5{ \mathrm{s}}^{-1}$ and $\beta$ particles at $3\times {10}^5{ \mathrm{s}}^{-1}.$ Mass number of substance is $234$ and take time for $1$ year as $3\times {10}^7 \sec .$ If mass of radioactive substance at that instant is $\mathrm{x}\times {10}^{-6} \mathrm{gm}$ find $x$ (Take Avogadro no. $=6\times {10}^{23}$) (Approximate the answer to the nearest integer.)