The company expected the advertising campaign to effect a change in average spending of more than $30. Test the compay's expectation by using the p-value method at the 5% significance level. You need to (a) justify your testing approach, (b) define any new notations properly, (c) state the null and alternative hypotheses, (d) show proper statistic for the test and steps of derivation, (e) make decision for the test and add a brief interpretation.