Nar

.....

0.61 is the answer

the good answer is E = 0.749401 notice that you can't make a person leave when the room is empty p(n,m) is the probability to find exactly n persons after m weeks p(n,m) = 0.6*p(n-1,m-1)+0.2*p(n,m-1)+0.2*p(n+1,m-1) with m>n>0 p(0,m) = 0.2^m p(m,m)= 0.6^m

iamnotnader you missed one point: when the room is empty you can't decrease the number of people to negative values. the answer must be bigger than 0.61