Organic Chemistry: Some Basic Principles and Techniques — Chemistry STD 11 Science — Question

$CH_3OH(l)+ \frac{3}{2} O_2 (g) $$\rightarrow CO_2 (g)+ 2H_2O(l)$

At $298\, K$ standard Gibb's energies of formation for $CH_3OH(l),H_2O(l)$ and  $CO_2 (g)$ are $-166.2,-237.2$ and $-394.4\, kJ\,mol^{-1}$ respectively. If standard enthalpy of combustion of methonal is $-726 \,kJ\, mol^{-1},$ efficiency of the fuel cell will be .......... $\%$.