Athree-cycle cascade refrigeration unit is to use methane (cycle 1), ethylene (cycle 2), and ammonia (cycle 3). the evaporators are to operate at: cycle 1, 112.6 k; cycle 2, 185 k; cycle 3, 255 k. the outlets of the compressors are to be: cycle 1, 3.5 mpa; cycle 2, 2.2 mpa; cycle 3, 1.2 mpa. use the peng-robinson equation to estimate fluid properties. use stream numbers from fig. 5.11 on page 212. the compressors have efficiencies of 70%.

a.) determine the flow rate for cycle 2 and cycle 3 relative to the flow rate in cycle 1.
b.) determine the work required in each compressor per kg of fluid in the cycle.
c.) determine the condenser duty in cycle 2 per kg of flow in cycle 1.