automata theory

Languages L_a, L_b, L_c and L_d are all regular languages. Using the properties of the Regular Languages prove/disprove the following statements: The set ((L_1)^c Intersection L_2)^c is a not a regular language. The set (L_a)^c Intersection (L_b)^R - (L_c Union L_d) L_a is a regular language. The set (L_a - phi) Union {lambda} a regular language. L = {a^n b^n: n > 0 & n