Which coefficient controls the product mass?

Calcium carbonate decomposes: $\mathrm{CaCO_3} \rightarrow \mathrm{CaO} + \mathrm{CO_2}$. Calculate the mass of carbon dioxide formed from 25.0 g of calcium carbonate. Use $M_r(\mathrm{CaCO_3})=100$ and $M_r(\mathrm{CO_2})=44$.