A mixture of 5 percent butane and 95 percent air is fed to a sieve-plate absorber containing eight ideal plates. The absorbing liquid is a heavy, nonvolatile oil with a molecular weight of 250 and a specific gravity of 0.90. The absorption takes place at 1 atm and 15°C. The recovery of butane is to be 95 percent. The vapor pressure of butane at 15°C is 1.92 atm, and the density of the liquid butane is 580 kg/m³ at 15°C. 

(a) Calculate the cubic meters of fresh absorbing oil per cubic meter of butane recovered. 

(b) Repeat, on the assumption that the total pressure is 3 atm and all other factors remain constant. Assume Raoult's and Dalton's laws apply.