A research company desires to know the mean consumption of milk per week among people over age 20 20 . They believe that the milk consumption has a mean of 4.5 4.5 liters, and want to construct a 99% 99% confidence interval with a maximum error of 0.09 0.09 liters. Assuming a standard deviation of 1.2 1.2 liters, what is the minimum number of people over age 20 20 they must include in their sample? Round your answer up to the next integer.