Ok mah, reasonable mah, I'm sure you were aware of the penalty
before you signed the letter right? Were you aware of the OT before
you signed? If you really cannot tahan beyond the 90 days, then
quit, but you should know you have to pay up, and not escape, since
you signed it and there is a binding agreement. You can find the
bestest lawyers in the universe, but if you signed and agreed to
it, no one can help you.
Give you the best option is to pay back the 1 month salary in
installments.