you have been pricing an mp3 player in several stores. three stores have the identical price of $800. each store charges 18 percent apr, has a 30-day grace period, and sends out bills on the first of the month. on further investigation, you find that store a calculates the finance charge by using the average daily balance method, store b uses the adjusted balance method, and store c uses the previous balance method. assume you purchased the mp3 player on may 5 and made a $100 payment on june 15. what will the finance charge for june be if you made your purchase from store a? from store b? from store c