Vern Corp. sold merchandise to a customer on credit. The invoice amount was $2,000; the invoice date was June 10 ; credit terms were 1/20, n/30. Wnicn one of the following statements is true? a. The customer must pay a $20 penalty if payment is made after July 9. b. The customer can take a $20 discount if the invoice is paid on July 10 . c. The customer should pay $2,000 if the invoice is paid on July 9. d. The customer must pay $2,020 if payment is made after June 20