Physics Question: Molar Specific heat: Constant volume?

A rigid iron cylinder contains propane gas. The cylinder and the gas are in thermal equilibrium. In a process, 8700 J of heat are transferred to the cylinder and the gas, so that at the end they are again in thermal equilibrium, with a temperature increase of 24 K. If the m of the cylinder is 0.51 kg, how many moles of propane are there in the cylinder?