Bathtub Woes

It was time for baths and showers. I told A it was his turn to go first.

A: It's not fair. I always have to put in the tub drain. How come I never can take a bath last one time and first the next time?
me: Just take your bath.
(a minute later)me: A, you took your bath second last time. Of course you have to put in the drain - you had to empty the tub last time.
A: Oh... yeah.