A laser printer is advertised to print text documents at a speed of 18 ppm (pages per minute). The manufacturer tells you that the printing speed is actually a Normal random variable with a mean of ppm and a standard deviation of ppm. Suppose that you draw a random sample of such printers.

Part i) Using the information about the distribution of the printing speeds given by the manufacturer, …find the probability that the mean printing speed of the sample is greater than ppm. (Please carry answers to at least six decimal places in intermediate steps. Give your …final answer to the nearest three decimal places).

Probability (as a proportion)

Part ii) Using the Normal approximation, which of the following is the probability that more than % of the sampled printers operate at the advertised speed (i.e., the printing speed is equal to or greater than 18 ppm)?

A.
B.
C.
D.
E.