The complete combustion of salicylic acid releases 21.90 kJ of energy per gram of salicylic acid. In a particular bomb calorimeter (initially at room temperature), the combustion of 0.1288 g of salicylic acid, in the presence of excess oxygen, causes the temperature of the calorimeter to rise by 1.36 °C. When a 0.3918-g sample of an unknown organic substance is similarly burned in the same calorimeter, the temperature rises by 3.60 °C. What is the energy of combustion per unit mass of the unknown substance?