Let f: R be defined by f(x)= [x], the greatest integer in x. Find f~l(B) for each of the following subsets B of R.
(a) B = {0, 1}
(b) B = {-1, 0, 1}
(c) B = [0, 1)
(d) B = [0, 2)
(e) B = [-1, 2}
(f) B = [-1, 0) U (1, 3}