Problem 9 Suppose you have the following regression equation: Y = g 4\" 31X + 6 and you are planning to use Z as an instrumental variable. 1. Why could it be a problem if R2 in the rststage equation is extremely low? 2. Why could it be a problem if the the R2 in the rst stage equation is 1? 3. . Assuming Z is a valid instrument. Suppose you ran the following OLS regression model. Would the coefcient on Z be positive, negative, or zero, and why? Y=50+1X+2Z+