2. Identify which of the following sets are open, which are closed, and which are neither. Sketch E in each case.

(a) E = {(x,y): X2 +4y2:::; I}.

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

( c ) E = {( X, y) : y ;::: x2, 0:::; Y < I}.

(

d) E = {(x, y) : x2 - y2 < 1, -1 < y < I}.