The sun can be treated as a spherical blackbody with a radius Rsun = 6.96 x 108 m and a surface temperature of Tsun = 5,780 K, emitting light uniformly outwards in all directions. Light from the sun travels a distance of d = 1.5 x 1011 m to reach the Earth before it is absorbed. The Earth itself acts as a blackbody and re-emits this absorbed energy into the surrounding space which is at an approximate temperature of Tsp = 50.0 K. According to this model, what is the equilibrium temperature of planet Earth? The radius of the Earth is Rearth = 6.38 x 106 m.