u may wish to refer to
this thread 
anyway the number of underwear to bring is up to you. u can always
wash ur clothing, or u can simply bring more. for the 3 wk
confinement, perhaps there is a need to bring more. but after that,
when u get to book out weekly, there wont be a need to, esp for PTP
when there is no outfied training.
feel free to post again if u haf any other questions or are still
not clear wat to bring! 