Complete combustion of ethane gives only gaseous products. In a closed vessel, 15 g of ethane and 112 g of $\mathrm{O}_2$ were allowed to completely react. What is the total number of moles of gaseous substances present in the vessel at the end of the reaction?

Consider the following

(A) 0.0025

(B) 500.0

(C) 2.0034

Number of significant figures in $A, B$ and $C$ respectively, are

1.84 g of a mixture of $\mathrm{CaCO}_3$ and $\mathrm{MgCO}_3$ is strongly heated to get a residue of 0.96 g . The percentage of $\mathrm{CaCO}_3$ in the mixture is