What amount of heat (in kJ) is required to convert 28.4 g of an unknown solid (MM = 67.44 g/mol) at -15.4 °C to a liquid at 42.7 °C? (specific heat capacity of solid = 1.95 J/g･°C; specific heat capacity of liquid = 1.18 J/g･°C; ∆Hfus = 5.72 kJ/mol; normal freezing point, Tempf = 28.3°C)