3. In the Department of Fisheries and Wildlife Conservation, an experiment was conducted to study the effect of stream characteristics on fish biomass. The regressor variables are as follows: average depth (of 50 cells), x; area of in-stream cover, X2; percent canopy cover (average of 12), x3; and area 25 centimeters in depth, x4. The response is y, the fish biomass. The data are as follows: Obs. X1 X2 X3 X4 y 1 14.3 15.0 12.2 48.0 100 2 19.1 29.4 26.0 152.2 388 3 54.6 58.0 24.2 469.7 755 4 28.8 42.6 26.1 485.9 1288 5 16.1 15.9 31.6 87.6 230 6 10.0 56.4 23.3 6.9 0 7 28.5 95.1 13.0 192.9 551 8 13.8 60.6 7.5 105.8 345 9 10.7 35.2 40.3 0.0 0 10 25.9 52.0 40.3 116.6 348 (a) Develop the multiple-regression equation and get it validated through 95% confidence estimate of the population slope between yield and each of the independent variables. (/5) (b) Use stepwise regression and best subset approaches, respectively, to further determine the best fitted regression model. (/5)