Qustion on PERT

Given the following estimates: Optimistic 3 days, Pessimistic 9 days, and most likely
6 days, what is the PERT weighted average?
A. 6
B. 4
C. 6.3
D. 6.1

PERT = (P + 4ML + O)/6

i also got 6
but the ans is C, seems the ans is wrong?
from www.certchamp.com

jep seems so

check again their calculation also gives answer as 6

Correct Answers are : 1 
Explanation : Optimistic = Co, most likely = Cm, Pessimistic = Cp. PERT weighted average = (Co + 4Cm + Cp)/6 = (3+4*6+9)/6 = 36/6 = 6

 

 

It must be 6 but we have found many dump has 6.3 as answer. I don't know why.