An experiment reported in Popular Science compared fuel economics for two types of similarly equipped diesel mini-trucks. Let us suppose that 12 Volkswagen and 10 Toyota trucks are: used in 90-kilometer per hour steady-spaced tests. If the 12 Volkswagen trucks average 16 kilometers per liter with a standard deviation of 1.0 kilometer per liter and the 10 Toyota trucks average 11 kilometers per liter with a standard deviation of 0.8 kilometer per liter, construct a 90% confidence interval for the difference between the average kilometers per liter of these two mini trucks. Assume that the distances per liter for each truck model are approximately normally distributed with equal variances.