You are in charge of constructing the Ferris wheel in each town a carnival visits. However, this is something you have never done before and you are getting different opinions from others on how long it takes. Joe, is new and has given you what you believe to be an optimistic estimate of 3 hours, Bill says it will take 10 hours, which seems too long to you and quite pessimistic. Lastly, Margie, who is the most experienced at this task is telling you it will take 8 hours. You are not sure who to believe, so you decide to do a PERT estimation, based on this you have determined it will take how many hours to assemble the Ferris wheel.
A. 7.5 hours
B. 8 hours
C. 21 hours
D. 7 hours