need the answer in ft/min, thanks!

Problem 5; 35 points) A stainless steel billet (k = 13 Btu/hr-ft-F, a = 0.24 ft/hr), 4 inches in diameter, is passing through a 20 ft . long heat-treating furnace. The initial billet temperature is 200 F. and it must be raised to a minimum temperature of 1650 F before working. The heat transfer coefficient between the furnace gases and the billet surface is 6 Btu/hr ft F. and the furnace gases are at 2200 F. At what maximum velocity (ft/min.) can the billet travel through the furnace and satisfy these conditions