The light energy that falls on a square meter of ground over the course of a typical sunny day is about 20 MJ . The average rate of electric energy consumption in one house is 1.0 kW . Part A got answer for part A and is correct
On average, how much energy does one house use during each 24 hr day?
Express your answer using two significant figures.
=86 MJ

Part B
If light energy to electric energy conversion using solar cells is 15%efficient, how many square miles of land must be covered with solar cells to supply the electrical energy for 250,000 houses? Assume there is no cloud cover. A=mi^2