6.19. Refer to Commercial properties Problem 6.18. Assume that regression model (6.5) for four predictor variables with independent normal error terms is appropriate. a. Test whether there is a regression relation; use a = .05. State the alternatives, decision rule, and conclusion. What does your test imply about B1, B2, B3, and B4? What is the P-value of the test? b. Estimate B1, B2, B3, and B4 jointly by the Bonferroni procedure, using a 95 percent family confidence coefficient. Interpret your results.