Acid rain caused by reaction of air pollutants with rainwater appears to be a growing problem in the northeastern United States. Pure rain falling through clean air registers a pH value 5.7(pH is measure of acidity (0 is acid; 14 is alkaline). Suppose water samples from 40 rainfalls are analyzed for pH, and x (bar) and s are equal to 3.7 and .5 respectively. For a 99% confidence Interval for the mean pH in rainfall, what is the width of the interval?