Laboratory data show that the time required to complete two chemical reactions in a production process varies.

Laboratory data show that the time required to complete two chemical reactions in a production process varies. The first reaction has a mean time of 50 minutes and a standard deviation of 4 minutes; the second has a mean time of 15 minutes an a standard deviation of 1 minute. The two reactions are run in sequence during production. There is a fixed period of 5 minutes between them as the product of the first reaction is pumped into the vessel where the second reaction will take place. What is the mean time required for the entire process?