6. (10 pts) You have obtained data on test scores and student-teacher ratios in region A and region B of your state. Region B, on average, has lower student-teacher ratios than region A. You decide to run the following regression Yi=BD + 31x1i+ 32x2i+l33x3i + \"E where xlis the class size in region A, 2:; is the difference in class size between region A and B, x3and is the class size in region B. Your regression package shows a message indicating that it cannot estimate the above equation. What is the problem here and how can it be xed? 7. (10 pts) Comment on the following statements: \"When X1 and X2 are correlated, the variance of 31 is larger than it would be if X1 and X2 were uncorrelated. Thus, if you are interested in [31, it is best to leave X2 out of the regression if it is correlated with X1.\