Expedia would like to test the hypothesis that the average roundtrip airfare between philadelphia and paris is higher for a flight originating in philadelphia when compared to a flight originating in paris. the following data summarizes the sample statistics for roundtrip flights originating in both cities. assume that the population variances are known. if population 1 is defined as flights originating in philadelphia and population 2 is defined as flights originating in paris, the 90% confidence interval for the difference in population means is