A popular flashlight that uses D size batteries was selected , and severa of the same models were purchased to test the "continous use life" of D batteries. To determine the continous use life of two D batteries, a fresh pair of D sized batteries were installed in a flashlight, the flashlight was turned on and the time noted. WHen the flashlight no longer produced light, the time was again noted. The resulting "life" data from the batteries had a mean of 22.5 hours. Assume these values have a normal distribution with a standard deviation of 1.58 hours.
A) What is the probablity that one randomly selected pair of batteries will have a test life between 20 and 24 hours?
B) What is the probablity that a randomaly selected sample of 49 pairs of batteries have a mean between 21 and 22 hours. Answer in complete sentences.