Norma has a credit card that uses the adjusted balance method. For the first 10 days of one of her 30-day billing cycles, her balance was $1850. She then
made a purchase for $160, so her balance jumped to $2010, and it remained
that amount for the next 10 days. Norma then made a payment of $930, so
her balance for the last 10 days of the billing cycle was $1080. If her credit
card's APR is 29%, which of these expressions could be used to calculate the
amount Norma was charged in interest for the billing cycle?