Benzene burns in oxygen according to the following reactions.
$C_6{H}_6\left(l\right)+\frac{15}{2}{O}_2\left(g\right)\to 3H_{2}O\left(l\right)+6C{O}_2\left(g\right)$ 
 If the standard enthalpies of formation of  $C_6{H}_6\left(l\right),H_{2}O\left(l\right)\text{ and }C{O}_2$ are 11.7,  $-68.1$ and $-94$ kcal/mole, respectively, the amount of heat that will liberate by burning 780 g of benzene is