A) Let A = {1, 2, 3, 4} and R a relations on A whose matrices is MR = [1 0 1 1 0 1 1 1 0 0 1 1 0. 1 1) Show that (A, R) is a poset (5 pts) 2) Find maximal, minimal, least and greatest if they exist (4 pts) B) Find the root and the height of (T, vo) where A = {1,2,3, 4, 5, 6} and T = {(1,4), (3, 2), (2, 1), (1, 5), (2, 6)} (Show your work) (5 pts) C) Evaluate the expression which is given in pre-order notation (4 pts) - x 54 +68 + 43