2.18 Carbon dioxide (CO2) gas within a piston-cylinder assembly undergoes a process from a state where p, = 5 lbf/in.², V, = 2.5 ft to a state where p2 =

20 lbf/in., V2 = 0.5 ft³. The relationship between pressure and volume during the process is given by p = 23.75 - 7-5V, where Vis in ft³ and pis in lbf/in.? Determine the work for the process, in Btu.