.) the quality control manager at a light bulb factory needs to determine whether the mean life of a large shipment of light bulbs is equal to 375 hours. the population standard deviation is 100 hours. a random sample of 64 light bulbs indicates a sample mean life of 350 hours. a.) (3) at the 0.05 level of significance, is there evidence that the mean life is different from 375 hours? b.) (1) clearly write down the test statistic (in notations) used for hypothesis testing. c.) (2) construct a 95% confidence interval estimate of the population mean life of the light bulbs. (clearly write down the formula used and the answer)