help me please!

Which additional information is needed to solve this problem?

Leelani wants to buy enough juice boxes so that each friend at her party can have three boxes. The boxes come in cartons of 12 boxes. Each carton costs $5.00. How much money will Leelani have to spend on juice boxes for her party?

A.
number of friends at party

B.
cost of one juice box

C.
number of boxes left over when the party is over