[25 points] It costs more to produce defective items as the must be scrapped and reworked, than it does to produce non-defective items. This fact suggests that manufacturers should ensure the qualityr of their products by perfecting the production process instead of depending on inspection of nished products. To better understand their metal stamping process, a manufacturer wants to estimate the mean length of items produced during the process within the past 24 hours. [2\" points]. a. How many parts should be sampled in to estimate the population mean within 0.1 mm with 90% confidence. Previous studies have indicated that the standard deviation of lengths produced is 2mm and that the lengths can be estimated by a normal distribution. h. If'management requires that the mean length be estimated within [1.] mm and that a sample size of no more than n= 100 be used, what is {approximately} the maximum condence level that can be attained