You might not need a database.
For the simplest case (an exercise for someone programming a couple of weeks) you don't need a database.
1- Create variables for the various amounts.
2- Have the user enter the amounts for each variable.
3- Do the math.
4- Make the decision
5- Display the result
(In this case, you don't really need the account number.)
A more advanced version might use a structure (AccountNumber.TotalCharged, etc)
Even more advanced - Use classes and objects (Each Account is an object.)
HINT - Next time, use a more descriptive title for your post.