How Much Power Does a Sphere with a Radius of 10

Multiple Choice

How much power does a sphere with a radius of 10 cm radiate if is has an emissivity e = 1.0 and is kept at a temperature of 400 K? The Stefan-Boltzmann constant is 5.67 x 10^-8 W/(m²·K⁴) .

A) 60 W
B) 70 W
C) 180 W
D) 210 W
E) 360 W