QUESTION 5 The length of life of an instrument produced by a machine has a normal distribution with a mean of 12 months and standard deviation of 3 months. a) If an instrument is selected at random, what is the probability that an instrument produced by this machine will last: i) less than 6 months. (3 marks) ii) between 8 and 14 months. (3 marks) b) Find the minimum length of life for 90% of instrument produced. (4 marks)