A pet food manufacturer has a facility with two lines that blend, can, and cook cat food. The production manager is curious whether there is a difference in the mean population amount produced by the lines. The manager randomly picks 300 daily production reports, 141 of which were for one production line and 159 of which were for the other. Assuming the population variances are unequal, a hypothesis test for the difference between the two population means would have how many degrees of freedom