To find the range you put group of numbers in order from smallest to largest.
Order for EASTERN... 90, 92, 111, 142, 305
Subtract 90 from 305 which equals 215
Order for WESTERN... 47, 84, 145, 372, 503
Subtract 47 from 503 which equals 456
The western cities are the largest so subtract 215 from 456 to find the difference which equals... 241
Answer is... 241 mi^2