Bill wants to replace the shingles on his roof. He goes to his local home-improvement store and finds that it costs $125 for 100 square feet of asphalt shingles. You can use a function to describe the cost of x square feet of shingles. Write an equation for the function. If it is linear, write it in the form h(x)=mx b. If it is exponential, write it in the form h(x)=a(b)x.