Myrtle has a credit card that uses the average daily balance method. for the first 21 days of one of her billing cycles, her balance was $2030, and for the last 9 days of the billing cycle, her balance was $1450. if her credit card's apr is 23%, which of these expressions could be used to calculate the amount myrtle was charged in interest for the billing cycle?
(a)- (0.23/365 x30)÷(21x $2030+ 9x$1450/30)
(b)- (0.23/365 x30)÷(9x $2030+ 21x$1450/30)
(c)- (0.23/365 x31)÷(9x $2030+ 21x$1450/31)
(d)- (0.23/365 x31)÷(21x $2030+ 9x$1450/31)