This is the equation. Try it for yourself and see if it works.
C= n x 4
Answer:
The area should be "210 cm to the second power"
Convert the percentage into a decimal


20% of 50 is 40
Store 1 : 12 paper towels for 3.60
3.60 / 12 = 0.30......30 cents per roll
store 2 : 10 paper towels for 3.50
3.50/10 = 0.35....35 cents per roll
the better deal is store 1 with paper towels costing 30 cents per roll