I agree with what all the other posters have said, this is an impossible task, but I tend to think that your dom knew this, and rather than have you spend much of any time working on it, he wanted an apology and a change of attitude and this unfeasible punishment was his way of hoping you'd realize this.

Of course not knowing the situation, this is just my impression: either you spend forever writing, or end up having to talk it out and take your real punishment. Sometimes what seems unreasonable is really a ploy to get you to see reason.

On another note, I've always fantasized about being set impossible tasks and then being punished for not completing them. It brings me to an entirely new feeling of helplessness...and consequently wetness.

Hope everything works for the best!

~ Reveler