Air (k = 0.028 W/m. K, Pr = 0.7) at 50°C flows along a 1-m-long flat plate whose temperature is maintained at 20°C with a velocity such that the Reynolds number at the end of the plate is 10,000. The heat transfer per unit width between the plate and air is
(a) 20 W/m

(b) 30 W/m

(c) 40 W/m

(d) 50 W/m

(e) 60 W/m