Cait purchases a $20 item at a store. She uses a coupon to receive a 15% discount and she pays 6% on the item. She calculates the total cost, in dollars, of the item using the expression shown.

Cait's expression: (1.15)(1.06)(20)

Part A: Describe the error in the expression Cait used for her calculation.

Part B: Show or explain how you would calculate the total cost of Cait's purchase.