A marketing research company desires to know the mean consumption of milk per week among people over age 37. They believe that the milk consumption has a mean of 2.3 liters, and want to construct a 80% confidence interval with a maximum error of 0.06 liters. Assuming a standard deviation of 1.4 liters, what is the minimum number of people over age 37 they must include in their sample? Round your answer to the nearest whole number.