2. [4 points] a) Are -11 and -13 congruent modulo 5? Explain. b) Can you find an n such that -11 = -13 mod n? If yes, what is n? If not, explain. 3. 4 points Simplify the following without adding and subtracting the initial numbers (a) (981 + 259) mod 11 = (b) (123 x 456) mod 11 =