Diesel fuel (C12H26) at 77F is burned in a steady flow combustion chamber with 20 percent excess

Question:

Diesel fuel (C12H26) at 77°F is burned in a steady flow combustion chamber with 20 percent excess air that also enters at 77°F. The products leave the combustion chamber at 800 R. Assuming combustion is complete determine the required mass flow rate of the diesel fuel to supply heat at a rate of 1800 Btu/s.