3. For the total population of students (which has millions of students). We take a sample of four students, whose ages are 10, 11, 12, and 15, and see that their GPAs are: 2, 3, 3, and 4, respectively. a. Use the Correlation formula to find r between Age and GPA in our sample. (You must show the steps to get the full credit) (10 points) b. Find the Regression Line Equation. ). (No steps necessary - just write the answer) (5 points)