In a fuel cell methanol is used as fuel and oxygen gas is used as an oxidizer. The reaction is $\mathrm { CH } _ { 3 } \mathrm { OH } ( \ell ) + \frac { 3 } { 2 } \mathrm { O } _ { 2 } ( \mathrm {~g} ) \rightarrow \mathrm { CO } _ { 2 } ( \mathrm {~g} ) + 2 \mathrm { H } _ { 2 } \mathrm { O } ( \ell )$. At 298 K standard Gibb's energies of formation for $\mathrm { CH } _ { 3 } \mathrm { OH } ( \ell ) , \mathrm { H } _ { 2 } \mathrm { O } ( \ell )$ and $\mathrm { CO } _ { 2 } ( \mathrm {~g} )$ 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\\
(1) $80\%$\\
(2) $87\%$\\
(3) $90\%$\\
(4) $97\%$