Let `A = {1, 2, 3}` & ` B = {2, 4, 6, 8}`. Let `R_1 = {(1, 2), (2, 4), (3, 6)}` and `R_2 = {(2, 4), (2, 6), (3, 8), (1, 6)}`, then find domains and range of relation `R_1` and `R_2`.