How to find the shape of distribution?

The shape of the distribution of the time required to get an oil change at a 10 - minute oil - change facility is Unknown. However, records indicate that the mean time is 11. 2 minutes, and the standard deviation is 3. 5 minutes (a) To compute probabilities regarding the sample mean Using the normal model, what size sample would be required? (b) What is the probability that a random sample of n = LO oil changes results in a sample mean time less than 10 minutes?