We want to estimate the average temperature of Earth using some basic principles.

At the location of the Earth, the intensity of thermal radiation from the Sun is approximately 1370W/m2
. The average distance between the Earth and the Sun is 1.496×1011 m.
Assume that the Earth reflects about thirty percent of the energy it receives from the Sun. This is called the albedo a of the Earth, where a=0.30
The questions are in the image file