Along 24 cm diameter shaft of stainless steel 304 (kstst = 13.72 w/m. k, rho = 7721 kg/m^3, cp = 490 j/kg. k) comes out from an oven at a uniform temperature of 636°c. the shaft is then exposed to a cross flow of air (ka = 45.89 w/m. k, rho = 0.6964 kg/m^3, cp = 1034 j/kg. k) at a velocity of 20 m/s and temperature of 218°c with a convection coefficient of h = 48.74 w/m^2.k. (a) how long does it take for the shaft to have a minimum temperature of 388°c? (b) calculate the maximum temperature of the shaft at that time as in part (a).