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 equal. Originating City
Philadelphia Paris
Sample mean $1,240 $1,060
Sample size 15 19
Sample standard deviation $270 $240

If Population 1 is defined as flights originating in Philadelphia and Population 2 is defined as flights originating in Paris, the degrees of freedom for this hypothesis test are

a. 33
b. 32
c. 34
d. 28