Assume that you have a sample of $n_1 = 9$, with the sample mean $\bar{X}_1 = 45$, and a sample standard deviation of $S_1 = 6$, and you have an independent sample of $n_2 = 16$ from another population with a sample mean of $\bar{X}_2 = 39$, and the sample standard deviation $S_2 = 7$. Construct a 99% confidence interval estimate of the population mean difference between $\mu_1$ and $\mu_2$. Assume that the two population variances are equal.
$\boxed{}$ ≤ $\mu_1 - \mu_2$ ≤ $\boxed{}$
(Round to two decimal places as needed.)