For each of the following, determine the number of degrees of freedom assuming equal population variances and

Question:

For each of the following, determine the number of degrees of freedom assuming equal population variances and unequal population variances.
a. n1 = 15, n2 = 15, s21 = 25, s22 = 15
b. n1 = 10, n2 = 16, s21 = 100, s22 = 15
c. n1 = 50, n2 = 50, s21 = 8, s22 = 14
d. n1 = 60, n2 = 45, s21 = 75, s22 = 10