The combustion of naphthalene (C10H8), which releases 5150.1 kJ/mol, is often used to calibrate calorimeters. A 1.05 - g sample of naphthalene is burned in a calorimeter, producting a temperature rise of 3.86 degrees Celsius. Burning a 1.83 - g sample of coal in the same calorimeter causes a temperature change of 4.90 degrees Celsius. What is the energy density of the coal?