3.a) In models (a)-(d) of question 1, what are the slope coefficients of X1 in each of the 4quarters? b) Suppose you estimate model (c) and wrote down the estimated

slope coefficients for X1 in each of the 4 quarters. You then estimate model (d) and write down the estimated slope coefficients for Xt in each of the 4 quarters. Do your estimates change? Why or why not?