Question

Manufacture of a certain component requires three different machining operations. Machining time for each operation is normally distributed and the three times are independent of one another. The mean values are 15, 30, and 20 minutes respectively. Their standard deviations are 1, 2, and 1.5 minutes respectively. What is the probability that it takes at least 1.5 hour of machining time to produce a randomly selected item

Answer 1