Suppose we have a linear regression model Yi=0+1Xi+ui a. [5 points ] Show that ESS=^12i=1n(XiX)2. b. [10 points ] Suppose the sample correlation coefficient between {Xi} and {Yi} is r. Show that the regression R2=r2. (Tip: use the result from Question (a)) c. [10 points] Suppose we reverse X and Y and have the following linear regression Xi=0+1Yi+i Show that if regression (1)'s R2=1, then ^1=1/1^. (Tip: use the result from Question (b))