Add formulas to ConvertCalculator form

I'm a wedding photographer and I've built a custom form where clients can get a price estimate for their wedding photo albums, which have several different options. I don't need any help building the form itself, but I do need someone to do the formulas to actually calculate the prices as this is lost on me. Unfortunately, I'm dyslexic and anything maths/sciencey is over my head. Hopefully it should be a simple and quick job for someone who understands it!