The right option for the mass of CO_2 produced by heating 20 g of 20% pure limestone is (Atomic mass of Ca =40 ) [ CaCO_3 → 1200 K CaO + CO_2]

The right option for the mass of $\displaystyle \mathrm{CO}_2$ produced by heating $\displaystyle 20$ g of $\displaystyle 20$% pure limestone is (Atomic mass of $\displaystyle \mathrm{Ca}=40$ ) $$\left[\mathrm{CaCO}_3 \xrightarrow{1200 \mathrm{~K}} \mathrm{CaO}+\mathrm{CO}_2\right] $$