In a sample of 60 electric motors, the average efficiency ( in percent) was 85 and the standard deviation was 2.a. Find a 95% confidence interval for the mean efficiency.b. Find a 99.5% confidence interval for the mean efficiency.c. What is the confidence level of the interval(84.63, 85.37)?d. How many thermostats must be sampled so that a 95% confidence interval specifies the mean to within +-0.35?e. How many thermostats must be sampled so that a 99.5% confidence interval specifies the mean to within +-0.35?f. Find a 98% lower confidence bound for the mean efficiency.g. The claim is made that the mean efficiency is greater than 84.6%. With what level of confidence can this statement be made?