A tep by step of the solution

The average number of miles (in thousands) that a car's tire will function before needing replacement is 66 and the standard deviation is 16. Suppose that 42 randomly selected tires are tested. Round all answers to 4 decimal places where possible and assume a normal distribution. a. What is the distribution of X? X ~ N( 66 b. What is the distribution of a? a ~ N( 2.4689 V c. If a randomly selected individual tire is tested, find the probability that the number of miles (in thousands) before it will need replacement is between 68.1 and 69.8. d. For the 42 tires tested, find the probability that the average miles (in thousands) before need of replacement is between 68.1 and 69.8. e. For part d), is the assumption that the distribution is normal necessary? O YesO No