1. A biologist is interested in knowing how the concentration of contaminant in a lake is changing after a chemical spill. The biologist takes several measurements of the concentration of contaminant after the chemical spill. After 4 hours, she measures 450 milligrams of contaminant per milliliter. After 12 hours, the concentration has decreased to 60 mg/ml. From the data she determines the linear model: y = -48.75x + 645. (a) Use technology to complete the table below (you may round values as needed): x= number of hours after the spill 2. 4 8. 10 12 14 16 y- concentration of contaminant (in mg/ml) (b) Use technology to create a good graph of the equation. The table you created in part (a) should help you find a suitable grid. Recall that a good graph has the following criteria: o The graph is easily visible and somewhat centered on the screen o All the x-intercepts and y-intercepts are clearly visible o Any other important features (e.g., peaks, valleys, gaps, etc.) are visible Once you have created a good graph, recreate a simple sketch below and be sure to specify the smallest and largest x-values and y-values of the window you used. Note: the Step1 instructions on page 62 instruct you to, "make a table with appropriate X-values." The problem above illustrates that, "appropriate x-values" may depend on the problem situation. Since there was no contamination before the spill, the table started at x=0 instead of at x =-10 (as you did in previous problems).