Situation A: the manager of a fast-food restaurant wants to estimate the average service time needed to take a customer's order. he records service time for 50 randomly selected customers and obtains a mean of 181.0 seconds and a standard deviation of 82.1 seconds.

suppose the manager decides to use a larger sample to find a more accurate confidence interval. how large of a sample would he need to estimatee the mean service time to within 10 seconds with 95% confidence? (Use the standard deviation of the sample as an estimate for the population standard deviation).