Mike is doing some holiday shopping. In most stores, he uses his bank card to pay. In some stores, he uses cash. Mike withdraws $80 cash from his account. The ATM receipt says his balance is $57.30. a) What was Mike's balance before he withdrew the cash? b) Mike makes a purchase of $18.48 using his bank card. What is his balance now? c) Mike is in line at another store with a sweater in his hand that costs $19.99. 

What is the after-tax cost of the sweater if Mike pays cash?