The demand function for good X is Qdx = a + bPx + cM + e, where Px is the price of good X and M is income. Least squares regression reveals that a = 5.25, b = - 1.36 c = -0.14, sa = - 6.19. sa = - 0.56, and sc = 0.05. The R-squared is 0.24. a. Compute the t-statistic for each of the estimated coefficients. b. Determine which (if any) of the estimated coefficients are statistically different from zero. c. Explain, in plain words, what the R-square in this regression indicates.