Mom: We should have taken my car.
Mom: Because my lumbar support is in that car.
Me: No it's not, and besides, where would we have put Jo in that car?
Mom: The trunk.
Me: I'll put YOU in the trunk.
Mom: That's fine because then I'd have my lumbar support.
Mom: Did you leave my lumbar support at home?
Me: No, it's in the trunk.
Mom, sounding victorious: Ergo if I was in the trunk I'd have my lumbar support.