Refer again to the data from the Gilmore Accounting firm found in the data file Gilmore (see Exercise 15-21).

a. Incorporate the client type into the regression analysis using dummy variables. Describe the resulting multiple regression estimate.

b. Test to determine if this model is useful in predicting the net profit earned from the client.

c. Test to determine if the number of hours spent working with the client is useful in this model in predicting the net profit earned from a client.

d. Considering the tests you have performed, construct a model and its estimate for predicting the net profit earned from the client.

e. Predict the average difference in profit if the client is governmental versus in manufacturing. Also state this in terms of a 95% confidence interval estimate.