4. A linear industry demand function of the form Q = a+ bP + cM + dPR was estimated using regression analysis. The results of this estimation are as follows: DEPENDENT VARIABLE: Q R - SQUARE F - RATIO P - VALUE ON F OBSERVATIONS: 24 0. 8118 28.75 0 . 0001 PARAMETER STANDARD VARIABLE ESTIMATE ERROR T - RATIO P - VALUE INTERCEPT 68 . 38 12. 65 5 . 41 0 . 0001 P -6. 50 3. 15 -2. 06 0. 0492 M 0. 13926 0. 0131 10.63 0 . 0001 PR -10.77 2. 45 -4. 40 0 . 0002 a. Is the sign of b as would be predicted theoretically? Why? b. What does the sign c of imply about the good? c. What does the sign of d imply about the relation between the commodity and the related good R? d. Are the parameter estimates a, b, c, and d statistically significant at the 5 percent level of significance? e. Using the values P = 225, M = 24,000, and PR = 60, calculate estimates of (1) The price elasticity of demand (E). (2) The income elasticity of demand (EM). (3) The cross-price elasticity (ExR). ing log-linear demand curve for a price-setting firm is estimated using the