The ceiling of a real number x, denoted by [xl, is the unique integer that satisfies the inequality 5. In words, [x] is the smallest integer that is greater than or equal to x. Answer the next two questions about the ceiling of a number a) Compute [O.11.I--1.71 and (6.3-15.7 +--4.811) 1 (1 mark) b) Prove or disprove that, for any real number x... if [xl x 2 1/2 then [2xl 2x]-1