The time in hours for a worker to repair an electrical instrument is a Normally distributed random variable with a mean of $\mu$ and a standard deviation of 50. The repair times for 12 such instruments chosen at random are as follows:

Part a) Find a 95% confidence interval for $\mu$. For both sides of the bound, leave your answer with 1 decimal place. ( , ).

Part b) Find the least number of repair times needed to be sampled in order to reduce the width of the confidence interval to below 26 hours.