A 1040 carbon steel specimen that has a tensile strength of 590 MPa and a yield strength of 375 MPa is to be used in an application where a safety factor of 3.5 is applied. Calculate the working stress for this specimen, in MPa.

Air (c-1.006 kj/kg.k, r-0.287 kj/kg.k) enters a nozzle steadily at 280 kpa and 77°c with a velocity of 50 m/s and exits at 85 kpa and 320 m/s. the heat losses from the nozzle to the surrounding medium at 20°c are estimated to be 3.2 kj/kg. determine (a) the exit temperature and (b) the total entropy change for this process. solve this problem using constant specific heats.