A sample of the sugar D-ribose of mass $0.727 \mathrm{~g}$ was placed in a calorimeter and then ignited in the presence of excess oxygen. The temperature rose by $0.910 \mathrm{~K}$. In a separate experiment in the same calorimeter, the combustion of $0.825 \mathrm{~g}$ of benzoic acid, for which the internal energy of combustion is $-3251 \mathrm{~kJ} \mathrm{~mol}^{-1}$, gave a temperature rise of $1.940 \mathrm{~K}$. Calculate the enthalpy of formation of D-ribose.
-1270