A manufacturing project has five independent phases whose completion must be sequential. The time to complete each phase is a random variable. The mean and standard deviation of the time for each phase are shown below.
(a) Find the expected completion time.
(b) Make a 2-sigma interval around the mean completion time (μ ± 2σ).

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Phase Mean (hours) Std. Dev. (hours) Set up dies and other tools Milling and machining Finishing and painting Packing and crating Shipping 20 10 14 4 48 6