Alternate to the tax problem in the book. (Annas, Andrew, Ariel, Beverly, and Chris D should do the tax problem in the book. Everyone else should do this problem.)

Ask the user how many cans of soda they will buy:
 
The base price for one can is $1.00
If you buy more than 30 cans, you get  $25 off the total of all the cans. 
If you buy more than 50 cans, every can has a 20% discount.
If you buy more than 100 cans, every can has a 30% discount.