For the following relations, find and list all the keys. 1. R1(A, B, C, D, E, F), F = {AC + D,BD + F} 2. R2(A, B, C, D, E, F), F = {ABC DEF, AB + A, BCD + EBF} 3. R3(A, B, C, D, E, F), F = {ABC EF,CD + AB} 4. R4(A, B, C, D, E, F), F = {ABCDEF, BD + C, AF DE} 5. R5(A, B, C, D, E, F), F = {ABC, BCD,CDE, DE F, EF + A}