List box

A parking garage charges a $6.00 minimun fees to park for upto 3 hours. the garage charge an additional $1.50 per hour for each hour of part thereof in excess of three hours. the maximun charge for any given 24-hours period is $25.00. Assume that no car parks for longer than 24 hours at a time. Write a program that will calculate and print the parking charges for each customer.

I am trying to do this in a list box but having problem. Any help will greatly be appreciated.

Might be better to post what you have and then folk can tell you where you are going wrong