2. Identify which of the following sets are open, which are closed, and which are neither. Find EO, E, and 8E and sketch E in each case.

(a) E = {(x, y) : x2 + 4y2 :s; I}.

(b) E = {(x, y) : x2 - 2x + y2 = O} U {(x, 0) : x E [2,3]}.

(c) E={(x,y):y~x2, O:S;y

(d) E={(x,y):x2-y2<1, -l