SECTION-B The first order rate constant for the decomposition of $\mathrm{CaCO}_3$ at 700 K is $6.36 \times 10^{-3} \mathrm{~s}^{-1}$ and activation energy is $209 \mathrm{~kJ} \mathrm{~mol}^{-1}$. Its rate constant (in s-1) at 600 K is $\mathrm{x} \times 10^{-6}$. The value of x is $\_\_\_\_$ . (Nearest integer) [Given $\mathrm{R}=8.31 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1} ; \log 6.36 \times 10^{-3}=-2.19,10^{-4} .79=1.62 \times 10^{-5}$ ]