To calculate per-square-foot usage for a house, divide total usage by square-foot area.
Estimating the averages (to either above or below the nearest tenth) for each house will suffice to select
the houses at which between 0.5 and 0.7 kWh per square-foot area were used during July:
House A: 0.7+ House B: 0.7-House C: 0.5+ House D:0.5-
As you can see, houses B, C, and D fall between 0.5 and 0.7 kWh.