An auditor for a hardware store chain wished to compare the efficiency of two different auditing techniques. To do this he selected a sample of nine store accounts and applied auditing techniques A and B to each of the nine accounts selected. The number of errors found in each of techniques A and B is listed in the table below: Errors in A Errors in B 27 13 30 19 28 21 30 19 34 36 32 27 31 31 22 23 27 32 Select a 99% confidence interval for the true mean difference in the two techniques. a) O [2.195, 6.693] b) O [1.084, 7.804] e) O [-3.113, 12,001] d) O [1.925, 6.963]