An array of power transistors, dissipating 5 W of power each, are to be cooled by mounting them on a 25cm X 25cm square aluminum plate and blowing air at 35 C over the plate with a fan at a velocity of 4m/s. The average temperature of the plate is not to exceed 65 C. Assuming the heat transfer from the back side of the plate to be negligible and disregarding radiation, determine the number of transistors that can be placed on this plate.