Air enters an open system with a velocity of 1 m/s and density of 1 kg/m3 at 500 k through a pipe with a cross-sectional area of 10 cm2 . the mass of air in the tank at a given instant is given by the expression m = 5p/t where p is in kpa and t is in k. if the temperature in the tank remains constant at 500 k due to heat transfer, (a) determine the rate of increase of pressure in the tank. (b) what is the sign of heat transfer, positive (1) or negative (-1)?