A manufacturer of floor mops would like his product to last 700 hours, on the average. He hopes the mean number of hours is not a lot less than 700 (people will not continue to buy his product) or a lot more than 700 (people would seldom have to buy the product). However, the manufacturer has reason to believe the mean may have changed. A random sample of 48 items shows that XÌ = 675 and s = 77 hours.

a- complete the test at the 5% level of significance.
b- what type of error may have been made?
c- what is the probability of committing this error?