I have to know what the reaction involving nitromethane this problem is referring to. Luckily, I've found a similar problem from another website, which is shown in the attached picture. So you won't be confused, I just highlighted with black the mass so that we focus on the given information here of 2.71 kg.
The ΔHrxn is given as -1418 kJ/mol of nitromethane. The molar mass of nitromethane is 61.04 g/mol. The solution is as follows:
Heat = (-1418 kJ/mol)(1 mol/61.04 g)(1000 g/1 kg)(2.71 kg)
Heat = -62,955.11 J