So Company 1 charges $6,000 dollars for 500 feet of fence.
Company 2 only charges $4500/500 or $9.00/foot up to 500 feet.
The difference of 6,000 - 4500 = $1,500 so using Company two you will get 60 more feet of fence then both companies break even. After 500 ft
Company 1 only charges $12.00 dollars a foot and Company 2 charges $25.00 a foot.
So if you need 500 ft Company 1 costs 6,000 + 391.80 tax
Company 2 costs 4,500 +293.85 tax
Question does not ask how many feet is going to be needed?