[@GrandMen]

6:35 I think there's a mistake as the avg waiting time will be 7.2 minutes instead of 4.8! Am I wrong?

[@KumarAnalytic]

Good explanation. Thanks sir

[@MauroReza]

I think there is an error on sec 20:54, should be 0+0+0+3+3+3+6+6+6+9

[@bonibonij]

I thought so too I think I'm wrong But I saw your comment. Thanks :D

[@davericardo2685]

excellent