the following questions based on the following regression equation (Standard errors in production, n=150): Qd=1000-50PA+10PB+.051,(20)(7)(.04) Where QD=quantity demanded of good A, PA=price of good A, PB=price of a competing good per capita income. For which of the following variables should a"two-tail" t-test be applied? a. I b. P c. PC d. Should be applied