Given the following information about a hypothesis test of the difference between two means based on independent random samples, which one of the following is the correct rejection region at a significance level of .05? ha: μa > μb, 1 = 12, 2 = 9, s1 = 4, s2 = 2, n1 = 13, n2 = 10.

a. reject h0 if t > 1.721.
b. reject h0 if t > 1.645.
c. reject h0 if t > 1.782.
d. reject h0 if t > 2.08.
e. reject h0 if t > 1.96.