Question for Movie Theater Goers

So, when I go to the movies and I spend $10.00 for a ticket and then I spend $27.50 for popcorn and a soda and I get to my seat, which arm rest is mine? Is it the one on the left, the one on the right or do I get half of both the right and the left?

I mean, the talking soda cup and the dancing popcorn box come on the screen and tell you the rules about cell phones and whatnot but never mention the armrest.

I asked the ticket taker and he didn't know but he was about 85 years old so he probably has more important things to think about.

Can somebody please answer this question?