Aresearcher wants to study the average lifetime of a certain brand of rechargeable batteries (in hours). in testing the hypothesis that the batteries duration is at least 1000 hours, a random sample of 25 rechargeable batteries is drawn from a normal population whose standard deviation is 200 and a sample mean of 940. use a significance level of 0.10. what is the hypothesis?
select one:
(a)- upper
(b)- lower
(c)- two