fine the same mean of the set of data. round your answer to the nearest tenth. the data below representsbthe amount of time several students spent taking a history test in minutes. 40,30,29,15,32,36,32,35,34,36

Can someone me and do the problem plz so i can understand it more better

We just started the introduction into circles and i have no idea how to do this.

Using pert, adam munson was able to determine that the expected project completion time for the construction of a pleasure yacht is 21 months, and the project variance is 4. a) what is the probability that the project will be completed in 17 months? b) what is the probability that the project will be completed in 20 months? c) what is the probability that the project will be completed in 23 months? d) what is the probability that the project will be completed in 25 months? e) what is the due date that yields a 95% chance of completion?