翻译一道英文出的数学题Phillip charged $400 worth of goods on his credit

翻译一道英文出的数学题
Phillip charged $400 worth of goods on his credit card. On his first bill, he was not charged any interest, and he made a payment of $20. He then charged another $18 worth of goods. On his second bill a month later, he was charged 2% interest on his entire unpaid balance. How much interest was Phillip charged on his second bill?
A. $8.76
B. $7.96
C. $7.60
D. $7.24
E. $6.63