You are correct. Think of it this way. You have two empty chairs. You have to select a female for one chair and a male for the other chair. How many different females can be placed in the one chair? Now, for each of those females, how many different males can be selected for the other chair? Do you see that for each female there are six choices to fill the other chair? And since there are five females, we have 5*6 different ways to select the leading roles.
