by the way, i'm confused :
if we answer the call of nature at the bathroom, we could use "at" ?
if we make up or do something else(such as take a bath...) in the bathroom, we could use "in"?
because i just think that take a bath will spend much time than just pee ...
so in+ long time ?
at+ short time?
i'm sorry, maybe you can't understand what i'm talking about, because i'm an english novice!