1-The amount of time required for an oil and filter change on an automobile is normally distributed with a mean of 45 minutes and standard deviation of 10 minutes. A random sample of 16 cars is selected. What is the probability that the sample mean will be sen 39 and 48 minutes? Question 2- if x is a normally distributed random variable with a mean of 19 and a variance of 4, p(8 < x < 13 " approx equals ? Question 3- a company that supplies reverse cycle air conditioning units has found from experience that 70% of the units it installs require servicing within the first 6 weeks of operation. In a given week the firm installs 10 air conditioning units. The probability that 5 of these 10 units require servicing within 6 weeks of operation is ? Question4- suppose x is normally distributed with variance Q power of 2= 16, and that p(x <30)= 0.8413. The mean u of X is