Dear Sir,
I have gone through your all requirements and visited your sample sites as well. As far as I understood, you are only required the working calculator as per your description. So my quote is for that.
But, your site has a lot of CSS gaps, so if you would like to cover those gaps. We will quote separately. Let me know, if you are interested, then discuss further to get started.
Hope to hear from you soon.
With lots of thanks an regards,
Ahmed T