Extracted text: Let X = {1, 2, 3, 4, 5, 6} and let T1 = {X, p, %3D {3}, {1,2,3}, {2,3,4}, {2}} and T2 = {X, þ, {2}, {1,2,3}, {4,5,6}), {2,4,5,6}} * T1 is a topology on X and T2 is not a topology on X T1 and T2 are both not topologies on O T1 and T2 are both topologies on X T1 is not a topology and T2 is a topology on X