In the Cash Discount $500 4/10 Net 30, the Number

In the cash discount $500 4/10 net 30, the number 10 refers to

A) the percentage discounted if the bill is paid within 30 days.
B) the percentage increase in price if the bill is not paid within 10days.
C) the number of days for which the discount is valid.
D) the discount in dollars per unit awarded if the order is paid on time.
E) the penalty in dollars in dollars if the bill is not paid within 10days.