There are 1000 sealed envelopens in a box,10 of them contain a cash prize of RS 💯 each 100 of them contain a cash prize of RS 50 each and every 200 of them contain a cash prize of RS 10 each and rest do not contain any rest do not contain any cash prize. If they are well shuffled and an envelope is picked up out , what is the probability that it contains no cash prize?