A research company desires to know the mean consumption of m

A research company desires to know the mean consumption of milk per week among males over age 45, They believe that milk consumption has a mean of 4.7 liters, and want to construct a 90% confidence interval with a maximum error of 0.09 liters. Assuming a standard deviation of 1.5 liters, What is the minimum number of males over age 45 they must include in their sample