Stainless steel ball bearings ( = 8085 kg/m3 and cp = 0.480 kJ/kgoC) having a diameter of

Stainless steel ball bearings (ƿ = 8085 kg/m3 and cp = 0.480 kJ/kg·oC) having a diameter of 1.2 cm are to be quenched in water at a rate of 800 per minute. The balls leave the oven at a uniform temperature of 900oC and are exposed to air at 25oC for a while before they are dropped into the water. If the temperature of the balls drops to 850oC prior to quenching, determine the rate of heat transfer from the balls to the air.