$10 \mathrm{~mL}$ of gaseous hydrocarbon on combustion gives $40 \mathrm{~mL}$ of $\mathrm{CO}_2(\mathrm{~g})$ and $50 \mathrm{~mL}$ of water vapour. Total number of carbon and hydrogen atoms in the hydrocarbon is _________ .

Consider the following reaction :

$$ 3 \mathrm{PbCl}_2+2\left(\mathrm{NH}_4\right)_3 \mathrm{PO}_4 \rightarrow \mathrm{Pb}_3\left(\mathrm{PO}_4\right)_2+6 \mathrm{NH}_4 \mathrm{Cl} $$

If $72 ~\mathrm{mmol}$ of $\mathrm{PbCl}_2$ is mixed with $50 ~\mathrm{mmol}$ of $\left(\mathrm{NH}_4\right)_3 \mathrm{PO}_4$, then the amount of $\mathrm{Pb}_3\left(\mathrm{PO}_4\right)_2$ formed is ________ mmol (nearest integer).