Exercises 2. The lifetime of computer chips is approximately normal with mean 1.4×106 hours and standard deviation 3×105 hours. The statistics department has 5 computers built with that chip as the main component. What is the probability that all 5 computers last longer than 1.8×106 hours? 3. A manufacturing process produces items whose weights are normally distributed. It is known that 22% of all the items produced weigh between 100 grams up to the mean and 40% weigh from the mean up to 190 grams. Determine the mean and the standard deviation.