1. Find all cluster points of each of the following sets.

(a) E = R \ Q.

(b) E = [a,b), a,b E R, a < b.

(c) E={(-l)nn:nEN}.

(d) E = {xn : n EN}, where Xn ---+ x as n ---+ 00.

(e) E={1,1,2,1,2,3,1,2,3,4, ... }.