The average grass maintenance engineer mows 1.4 acres of grass per day in Barron, Montana. Because labor costs are increasing, the city decides to try a new brand of mower. Ten randomly selected engineers are given these new mowers. After a test period, these 10 engineers cut an average of 2.1 acres per day, with a standard deviation of .6 acre. If the costs are similar, should the city purchase more new mowers?