Duration calculation for Activities

[Binoy]

I was referring Andy Crowe's book, and I found an intersting fact. If Early Start and Early Finish of an activity is given as the same, duration of the activity is 1. If it is calculated in days, it means that the activity starts in the beginning of the day and end at EoD. So duration calculation should be ES-EF+1. I thing the other formulas remains the same.