please assume nonideal gas

Question 2: A steel cylinder contains ethylene (C2H4) at 200psig. The cylinder and gas mass is 372lbbm. The supplier refills the cylinder with ethylene until the pressure reaches 1000 pisg, at which time the cylinder and gas mass is 400lbm. The temperature is constant at 25C. [12] Calculate; a) the charge to be made for the ethylene if the ethylene is sold at BD 0.5 per pound b) the mass of the empty cylinder c) the volume of the empty cylinder in cubic feet. (Assume non ideal gas)