In order to check for gender bias in a standardized national achievement test, researchers compared the means of random samples of scores for male and female students. The sample mean of the387scores for males was231with a sample standard deviation of82. The sample mean of the413 scores for females was241with a sample standard deviation of74.

Assuming the population variances are equal and using the pooled estimate of the standard deviation, a hypothesis test for the difference between the two means would have how many degrees of freedom?