73. Prove or disprove each of these statements about the floor and ceiling functions. a) . b) L2x= 21xwhenever x is a real number. c) 1 + -(x + Lx]l - Lx] for all real numbers x yl 0 or 1 whenever x and y are real numbers. d) ]-(x1 for all real numbers x and y. x1 for all real numbers r