Answer:
Cost is proportional to area:
Carpet that costs $22 for every 3 square yards.
Mulch that costs a set amount to cover a square foot.
The table
The Graph
Cost is NOT proportional to area:
Asphalt sealant that is quoted at a set price per square foot, plus a labor fee.
Not enough information:
A wood deck quoted at a bulk cost for 25 square feet.
