Chase is trying to calculate the total cost of the T-shirt that he's buying. Since it's on sale, he first found the amount of the discount and added that to the original price. Next, he subtracted off the amount of the sales tax. His total, though, is different than the sales clerk's total. What did Chase do wrong?

a. He should have subtracted the discount.
b. He should have added the sales tax.
c. He should have subtracted the discount and added the sales tax.
d. Nothing. The sales clerk has the wrong total.