Determine a a in each case. (a) a = (0, 1] in the lower limit topology on r. (b) a = {a} in x = {a, b, c} with topology {x, ø, {a}, {a, b}}. (c) a = {a, c} in x = {a, b, c} with topology {x, ø, {a}, {a, b}}. (d) a = {b} in x = {a, b, c} with topology {x, ø, {a}, {a, b}}. (e) a = (-1, 1) u{2} in the standard topology on r. (f) a = (-1, 1) u{2} in the lower limit topology on r. (g) a = {(x, 0) erp | xer} in r2 with the standard topology.