the statement says "He has identified 10 stakeholders with whom he needs to communicate"...he cannot communicate with himself, so it makes sense to add him too rather than he including himself identified 10 stakeholders.
I would consider the key word stakeholders it includes all members in the project including PM. So i would calculate 10+3-1=12 members and apply the formula n(n+1)/2 = 12(12-1)/2= 66
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