Let X = {1, 2, 3, 4}. Determine which of the following are topologies on X: (a) T = {{1}, {2}, {3}, {4}}. (b) T = {∅, {1, 2, 3, 4}}. (c) T = {∅, {1}, {1, 2}, {1, 2, 3}, {1, 2, 3, 4}}. (d) T = {∅, {1, 2}, {2, 3}, {1, 2, 3}, {1, 2, 3, 4}}. (e) T = {∅, {2}, {1, 2}, {2, 3}, {1, 2, 3, 4}}. (2) List all of the topologies on X = {1, 2}. (3) Prove that the following set is NOT a topology on R: T = {∅, R} ∪ {(0, n) : n ∈ N}.