John works as a project manager for you certified Inc. He's working on a project with his team members for completing a project activity. For the activity, the team members notified John that the activity is most likely to be completed in 15 days. However, in the worst case, it may take 25 days, and if all conditions are favorable, it might be completed in 10 days. Which of the PERT estimate of the activity? A. 16 B. 11 C. 13 D. 23