Silvertone Corp. sold merchandise to a customer on credit. The invoice amount was $1,000; the invoice date was June 10; credit terms were 1/10, n/30. Which one of the following statements is true?
a) The customer can take a $10 discount if the invoice is paid on June 30
b) The customer should pay $1,000 if the invoice is paid on July 9
c) The customer must pay a $10 penalty if payment is made after July 9.
d) The customer must pay $1,010 if payment is made after June 20.