Sir i am stuck for this question

1. A machine produces components whose lengths in centimetres have a mean 6.50 and standard deviation 0.024. The specification limits for an average of 100 lengths are given as 6.50 4: 0.005. What percentage of averages of 100 components will have lengths outside these limits? On a certain period, 10% of averages of 100 components are observed to be defective (i.e. have lengths outside the limits). If the process has become more variable, but the mean is unchanged, find the new standard deviation (of the original variable and the individual component) 2. The annual rainfall in inches in a certain region is modelled by a normal random variable with mean 40 and variance 16. What is the probability that it will take at least 5 years before a year occurs having a rainfall of over 45 inches? What assumptions are you making