The spectral emissive power $$E_1$$ ; for a diffusely emitting surface is $$E_1 = 0 for \lambda < 3\mu m; E_1 = 150 W/m^2 \mu m for 3 < \lambda < 12 \mu m; E_1 = 300W/m^2 \mu m for 12 < \lambda < 25 \mu m; E_1 = 0 for \lambda > 25 \mu m.$$ The total emissive power of the surface over the entire spectrum is

A

$$1250 W/m^2$$

B

$$2500 W/m^2$$

C

$$4000 W/m^2$$

D

$$5250 W/m^2$$