Roger has an unpaid balance on his credit card.His credit card is on a 30 day cycle, i.e. a bill for the credit card balance is to be paid every 30 days.For the first 10 days of the billing cycle the balance on Roger's credit card is $300.The balance on Roger's credit card for the next 10 days in the cycle is $400, and the balance on his credit card for the last 10 days of the cycle is $500.If the credit card has a 20% annual interest rate, the interest charged for the current 30 day cycle will be

a. $5.

b. $6.67.

c. $8.33.

d. $80.