TOPIC: network diagram

Kindly take look at this question and clarify accordingly:
The activity “Ship Container” in your network diagram has an early
start of day 17, a late start of day 22 and a late finish of day 37. What is the activity duration?
A.) 15 days
B.) 16 days - Correct Answer
C.) 59 days
D.) 14 days

Based on the Formula guide the formula says Activity Duration=EF - ES + 1 or LF - LS + 1..when translated AD= 37-22+1 = 16. Based on Rita 6th Edition the answer will be 15 because ES = 0.

kindly clarify this confusion.

I'd really like the answer to this as well. You only get one correct answer on the test. I use Rita's book as well. Do we use base "0" or base "1" for calculations? The can't both be correct. Which one does PMI want?

I came across the same question. From the network diagram node, i know its answer should be 15. But why is it 16?

What is PMI specific answer for this? Why do we add a "1" to activity duration? Because when i draw my network diagram for my projects, for e.g. if duration is 5 days and activity LS is 20th May i consider LF to be 24th and not 25th May.