Xin goes to a store and buys an item that costs xx dollars. She has a coupon for 10% off, and then a 7% tax is added to the discounted price. Write an expression in terms of xx that represents the total amount that Xin paid at the register.
a. 1.07 * (0.9 * xx)
b. 1.1 * (1.07 * xx)
c. 0.9 * (1.07 * xx)
d. 0.93 * xx
