At $25^{\circ} \mathrm{C}$ and 1 atm pressure, the enthalpy of combustion of benzene (1) and acetylene (g) are $-3268 \mathrm{~kJ} \mathrm{~mol}-1$ and -1300 kJ mol-1, respectively. The change in enthalpy for the reaction
$3 \mathrm{C}_2 \mathrm{H}_2(\mathrm{~g}) \rightarrow \mathrm{C}_6 \mathrm{H}_6(\mathrm{I})$, is