Q: If lst1 is empty, what is the result of interleaving lst1 and lst2?
A: lst2
Q: If lst1 and lst2 are not empty, and we begin with the first card of lst1, what is the result of interleaving lst1 and lst2?
A: The result of consing the head of lst1 onto the result of interleaving lst2 and the tail of lst1