Business experts and case studies needed!

I'm writing a couple of articles for the Amex website and I need an SME case study and a business expert for each of them:

1, How to calculate ‘payback period"
2, Net present value: formula, definition and examples

Are you a business that uses either of these, can you talk about why the formula or calculation is important / beneficial for you? 

Are you an expert (maybe an adviser, consultant or accountant) that can talk about either of these?

Please drop me a line if you can help and I can explain further! ruth.emery.freelance@gmail.com.

(Note the case studies need to accept Amex. This is where the articles are published: https://www.americanexpress.com/en-gb/business/trends-and-insights/)