Part of the learnings in doing a research project is learning how to find this information himself!

I am sure his best resource is the web, perhaps he needs someone who speaks spanish to help him get information from gov websites here...? Remember also that this is the DR, and the stats that you will get on the country may vary greatly from source to source. Good luck with the research.
The only thing I am going to give you is that the largest is Santo Domingo, and it is the capital.
marc