4. a) In the Bertrand model with product differentiation, suppose that the two Bertrand firms face the following symmetric demand curves: 9 = 12- P1 + P2 92 = 12- P2 + PI where 91, 2 20 and P1, P2 12. Also assume that MC = AC = MC, = AC, =0 1 ) Draw the price reaction functions and find the Bertrand equilibrium. (1+1+2=4 points) ii ) How does product differentiation affect the "Bertrand paradox"? (2 points)