Calculating break-even point - TonTon app for iPhone and iPad

This is an app for calculating the break-even point used in managerial accounting.

When should this app be used?
It should be used when you wish to make your business more efficient by clarifying expenses.

For example:
Consider a business that sells hamburgers for ¥100 a piece. Its expenses are divided between costs that do not change regardless of how many hamburgers are sold, such as rent and labor costs (fixed costs), and the costs that go into making a hamburger, such as the cost of bread, cheese, and pickles (variable costs).
How many hamburgers must be sold in order to cover the rent and labor costs?
This application will calculate that answer.

Caution
In the event that you do not know whether a cost is fixed or variable, please do your best to categorize it as one or the other anyway. The purpose of this app is to clarify, and if the categorization is imprecise, the break-even point will be imprecise as well.