80 g of calcium carbonate is heated strongly.

Step 1. (a) $80\ \text{g} - 44.8\ \text{g} = 35.2\ \text{g}$ of carbon dioxide.

Step 2. The share. $\dfrac{44.8\ \text{g}}{80\ \text{g}} = 0.56$ of the carbonate becomes calcium oxide.

Step 3. (b) $0.56 \times 250\ \text{g} = 140\ \text{g}$.