You have been pricing Samsung-Galaxy SmartWatch in several stores. Three stores have the identical price of $500. 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 using the previous balance method. Assume you purchased the SmartWatch on May 5 and made a $100 payment on June 15.