A researcher conducted a study comparing the scores of two independent group. Group A had an n = 30, a sample mean of z = 20.8 , and a sample standard deviation of = 6.0. Group B had an n = 20, a sample mean of I = 15.9, and a sample standard deviation of $ = 4.0. Assuming equal variances between the groups, calculate the lower bound of a 95% confidence interval of the difference in population means between Group A and Group B