Chemical and manufacturing plants sometimes discharge toxic-waste materials such as DDT into nearby rivers and streams. These toxins can adversely affect the plants and animals inhabiting the river and the riverbank. The U.S. Army Corps of Engineers conducted a study of fish in the Tennessee River (in Alabama) and its three tributary creeks: Flint Creek, Limestone Creek, and Spring Creek. A total of 144 fish were captured, and the following variables were measured for each: 1. The number of miles upstream from the river 2. Length (centimeters) 3. Weight (grams) 4. DDT concentration (parts per million) These data are saved in the DDT file. a. Fit a multiple linear regression model to the data, where y = DDT level, x] = mile, x2 = length, and x3 = weight. Report the least squares prediction equation. b. Conduct a test of the global utility of the model. Use a = .05