Consider the following relations on {a, b, c,d}: R1 = {(a,a), (a,b), (b,b), (b,c), (c,c), (c,d)} R2 = {(a,a), (a,b), (a,c), (b,b),(b,a), (c,d),(d,d)} R3= {(c,d),(d,c)} R4 = {(a,c), (c,c)} Which of these relations are reflexive? Justify your answer. Which of these relations are symmetric? Justify your answer. Which of these relations are antisymmetric? Justify your answer. Which of these relations are transitive? Justify your answer