It is assumed that the lifetime, in hours, of 60 Watts bulbs obeys a normal distribution of variance 625 hours2. We extract a random sample of 20 bulbs. The average life of these bulbs is 1014 hours. 1. Construct a 95% confidence interval for the average life of the bulbs. 2. If, from this sample, we have constructed a confidence interval whose amplitude (length) corresponds to 8 hours, what is the confidence level of confidence level of this interval? 3. If, for a future experiment, we would like to be 95% sure that the error in estimating the average life of the bulbs will be less than 5 hours, what should be the sample size used?