In one stage of an annealing process, 304 stainless steel sheet is taken from 300 K to 1250 K as it passes through an electrically heated oven at a speed of V_s = 10 mm/s. The sheet thickness and width are t_s = 8 mm and W_s = 2 m, respectively, while the height, width, and length of the oven are H_o = 2 m, W_o = 2.4 m, and L_o = 25 m, respectively. The top and four sides of the oven are exposed to ambient air and large surroundings, each at 300 K, and the corresponding surface temperature, convection coefficient, and emissivity are T_s = 350 K, h = 10 W/m² ∙ K, and ε_s = 0.8. The bottom surface of the oven is also at 350 K and rests on a 0.5-m-thick concrete pad whose base is at 300 K. Estimate the required electric power input, P_elec, to the oven.