You are a xenoanthropologist studying the alien planet of Mintaka IV. On Mintaka IV, there are two species of aliens - Xorts and Yokks - and there are two continents - Algorf and Blorgon.

Xorts from Algorf always tell the truth, while Xorts from Blorgon always lie. On the other hand, Yokks from Algorf always lie, while Yokks from Blorgon always tell the truth.

You are speaking to a group of 13 aliens, but you don't know what species they are or where they're from.

You ask each of them "are you a Xort?" and 8 say "yes". 

You ask each of them "are you from Algorf" and 5 say "yes".

You ask them another question - to which the answer can only be yes or no - and 4 say "yes". On the basis of this information, you are able to deduce the species and continent of each alien.

What question might you have asked, and how many are Yokks from Blorgon?

(There are many possible answers to this question - you might like to submit more than one!)