Math! First to answer (correctly) gets 10 points?

In 2000, the United States Postal Service charged 34 cents for the first ounce of first class mail, and the cost for each additional ounce was 21 cents. The equation

C = 21w + 13

can be used to determine C, the total cost in cents, for mailing w ounces of first class mail.

Gina has $6.25 and wants to know if she has enough money to mail a package. Which equation should she use to find out how many ounces of first class mail she can afford to send?

answer choices:

A. w =

B. w = 21C + 13

C. w =

D. w = 21C − 13

thanks :)