A large accounting firm tests a new software with 10 randomly selected employees. It measures the time that the employees take in finishing a particular type of task with the existing software in use and then measures the time that they take with the new software. They compute the difference d=(new - old) for each of these 10 employees to be able to estimate . d In the comparison, they find that the mean of these differences is -67 minutes and standard deviation 12 minutes. Construct a 95% confidence interval for d the mean of such differences for the entire population of their employees. Assume a normal population.