Gudenas Company makes a credit card sale to a customer for $500. The credit card sale has a grace period of 30 days and then an interest interest charge of 18% per year or 1.5% per month is added to the balance. If the unpaid balance on the above sale is $300 at the end of the grace period, the interest charge is:
a) $3.00.
b) $5.00.
c) $4.50.
d) $7.50.