
Kamal Sir I am a Big fan of yours Please help me out with the question 
If we have an empty room, and every week there is a 0.6 probability for a person to join, 0.2 probability for a person to leave, and 0.2 probability for no change (only one action can be performed per week), what is the probability that there are at least 40 people in the room after 104 weeks?
(A) 0.42
(B) 0.55
(C) 0.61
(D) 0.67
(E) 0.74
Please explain how you do it, thanks!
Sir I know that IT would be done by unions and intersections but please guide me and it is some what with atleast 40 in 104 weeks so ?
Sir I also want to join in the CBT club I am dying to join it
Thanks
Regards
Anuj 