Using Ajax, I need to do the following:

1) Create a page that will have a simple calculator that does the four main operations (add, subtract, divide, multiply) 2) Create 3 text boxes (first number, second number, result) 4 buttons one for each operation.

Add additional button to clear the results

3) Prevent dividing by zero

4) Explain callback feature, give me an example explaining callback

5) Create the functions as a web services