For the next several problems, consider the following population regression model Y = Bo+B1X+Z + (1) where Y is a students grade point average, X is class size, and Z is parental income. Suppose X and Z are negatively correlated. Further suppose neither B1, B2 are equal to zero. 8. Cov(X,Y) == var(X) 9. In order for the regression coefficients to be unbiased, must assume = 0 for all values of X and Z. In addition to model (1), also consider the following regression: 10. >