When should we use responsive, mobile or app design?

[Saya]

I was in a conference and a business owner approached me with above question.
He wanted to know " Is it better to save money and just make ONE responsive design or have three, web, mobile and app design all?
When we need to create three of them?
In response I wrote an article is hard to copy it here.
You can read it here:
http://designs4ux.com/when-should-we-us ... -mobile-...
If you have more ideas and suggestion please share.