Solid fuel used in rocket is a mixture of ${\mathrm{Fe}}_2{\mathrm{O}}_3$ and Al (in ratio 1:2). The heat evolved   per gram of the mixture is _______(Nearest integer)
Given:  ${\mathrm{\Delta H}}_{\mathrm{f}}^{\mathrm{\theta }}\left({\mathrm{Al}}_2{\mathrm{O}}_3\right)=-1700\hspace{0.17em}\mathrm{kJ} {\mathrm{mol}}^{-1}$
${\mathrm{\Delta H}}_{\mathrm{f}}^{\mathrm{\theta }}\left({\mathrm{Fe}}_2{\mathrm{O}}_3\right)=-840\hspace{0.17em}\mathrm{kJ} {\mathrm{mol}}^{-1}$
Molar mass of Fe, Al and O are 56, 27 and 16 $\mathrm{g}{\mathrm{mol}}^{-1}$ respectively