A binary relation R on a set A is irreflexive if and only if, for every aA,(a,a)/R. 1. Which relations in Exercise 2.19 are irreflexive? 2. Can a binary relation be neither reflexive nor irrefelexive? Consider binary relations on the set A={a,b,c,d}. Are the following relations reflexive? Symmetric? Antisymmetric? Transitive? 1. R1={(b,b),(b,c),(b,d),(c,b),(c,c),(c,d)} 2. R2={(a,a),(a,b),(b,a),(b,b),(c,c),(d,d)} 3. R3={(d,b),(b,d)} 4. R4={(a,b),(b,c),(c,d)} 5. R5={(a,a),(b,b),(c,c),(d,d)} 6. R6={(a,c),(a,d),(b,c),(b,d),(c,a),(c,d)}