[ad404b8a372f2b9]

It's odd to me that anyone would come up with 3, to me it was immediately very apparent from the diagram that the closest answer was 9/2.

[HarHarVeryFunny]

I guess if you're smart enough to realize that 4 is the right answer, but isn't one of the choices, then the next question is "what were they thinking?", which is why 3 would be the smart guess to get your answer marked as correct.