In a fuel cell, methanol is used as fuel and oxygen gas is used as an oxidizer. The reaction is:

${\mathrm{CH}}_3\mathrm{OH}\left(\mathrm{l}\right)+\frac{3}{2}{\mathrm{O}}_2\left(\mathrm{g}\right)⟶{\mathrm{CO}}_2\left(\mathrm{g}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

At 298 K standard Gibbs energies of formation for ${\mathrm{CH}}_2\mathrm{OH}\left(\mathrm{l}\right),{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$ and ${\mathrm{CO}}_2\left(\mathrm{g}\right)$ are $-166.2, -237 .2$ and $-394.4 \mathrm{kJ} {\mathrm{mol}}^{-1}$ respectively. If standard enthalpy of combustion of methanol is $- 726 \mathrm{kJ} {\mathrm{mol}}^{-1}$, efficiency of the fuel cell will be :