Your calculator project sounds interesting. However, some more information would be appreciated before an accurate bid can be made.
If you have an NDA to sign that would enable you to provide that information, then please send it through. Otherwise, I can supply an NDA if you need.
FYI - in this case I would draft for European practice if that is your preference. Given that European patent laws are generally more stringent than elsewhere (including the US) then it should be suitable for for ease of downstream processing of your patent application.
The only skill listed for this project is 'patents'. If you need more than a patent specification drafted then please let me know.
Thomas