Check each person's claim by asking whether that person could actually be the truthful, interested one making it; zero and four collapse immediately under their own weight.
Mr Basu asks five people, Asit, Barun, Chandra, Danny and Eshita, whether they are interested in a new project. Their replies each name a different total: Asit says none are interested, Barun says one, Chandra says two, Danny says three, and Eshita says four. Mr Basu knows that anyone interested always tells the truth and anyone not interested always lies. We need the actual number of people interested.
With Asit, Barun, Chandra and Eshita all ruled out as liars, Danny's claim that three people are interested is the one statement left standing.
Let's summarize:
So three of the five people are interested in the new project.