comma before second 'and' [conjunction]: experts and scientists, and

[Memar]

I estimated travel expenses for 5 experts and scientists, and 3 staff.

Do I need the after the word scientist. What is the right way of using and in the above sentence (5 expert and scientists all together)

Thansks for your time and help

 

[Frank Smith]

I would ditch the comma in favour of a hyphen:
"for 8 people - 5 experts and scientists plus 3 staff" (Using "plus" to avoid repetition and confusion of a second "and""
However your sentence is fine as it stands. Maybe to make it clearer, you can start it with "For a total of 8 people, I estimated..." OR end it with "totalling 8 people".

 

[Frank Smith]

Or simply change the second "and" to "plus"

"I estimated travel expenses for 5 experts and scientists plus 3 staff." No comma needed.