Calculation in code behind

Question

Chauffeur service cost $30. It is an option to user whether they want the service or not. When they already select car, and day of rental, I store it in session.

Answer 1

Why don't you create a custom class, add the properties like Car, Price, Day, ChaffterUsed etc. Create the object of the class, fill the properties and store the object into session. On next page, load the object from session and use it.