A Linde-type air liquefaction system is used in a certain facility.

The energy consumption of the plant is 109 kcal/kg of fed air.

The liquefied fraction turns out to be 20% when 15 kcal/kg of refrigeration is used, and 29% when using 25 kcal/kg of refrigeration.

Assume that the loss of energy is a constant fraction of the refrigeration. The nonliquid air exits at 290K and 1 atm. Determine the operating pressure and the design pressure of the compressor, and also its efficiency.