sheet for calculations

Hi peeps. I have tried searching a bit for what I am looking for but its hard to put a name or keyword, I ma sure you guys will come up with it straight away.

If you look at the excel file, I need to fill in the options and have a total generated. I have no idea how to do this. I guess its a kind of referencing to other cells.

I think this is way more simple than I have made it out to be. Hopefully you peeps can help me out, I will attach the file, this will give you a better idea I think.

CHeers!
Mike