Efficient manufacturing: Efficiency experts study the processes used to manufacture items in order to make them as efficient as possible. One of the steps used to manufacture a metal clamp involves the drilling of three holes. In a sample of 85 clamps, the mean time to complete this step was 60.4 seconds. Assume that the population standard deviation is o = 12 seconds. Round the critical value to no less than three decimal places. Part 1 of 2 (a) Construct an 80 % confidence interval for the mean time needed to complete this step. Round the answer to at least one decimal place. An 80 % confidence interval for the mean is 58.7