10.56 Determine the p-value for the following hypothesis tests for the difference between two means with population variances unknown.

a. Ha: 1  2  0, n1  6, n2  10, t  1.3

b. Ha: 1  2  0, n1  16, n2  9, t2.8

c. Ha: 1  2  0, n1  26, n2  16, t  1.8

d. Ha: 1  2  5, n1  26, n2  35, t1.8