4. The lifetime of a certain brand of laptops has normal distribution with the mean of 6.2 and standard deviation of 3 years. А. If we take a random sample of size 100 laptops of this brand, what is...

Extracted text: 4. The lifetime of a certain brand of laptops has normal distribution with the mean of 6.2 and standard deviation of 3 years. А. If we take a random sample of size 100 laptops of this brand, what is the probability that their sample average lifetime will be between 5 and 9 years. Is the probability you obtain here exact or approximate? Explain. В. will need to be serviced or replaced while under warranty? What should the manufacturer have as a warranty so that at most 10% of their laptops