At cruise conditions, air flows into a jet engine at a steady rate of 65 lbm / s 65 lbm/s. Fuel enters the engine at a steady rate of 0.60 lbm / s 0.60 lbm/s. The average velocity of the exhaust gases is 1500 ft / s 1500 ft/s relative to the engine. If the engine exhaust effective cross‐sectional area is 3.5 ft 2 3.5 ft2, estimate the density of the exhaust gases in lbm / ft 3 lbm/ft3.