Decide if the following statements are true or false. Justify your answer.
a) If p is prime, then 22p - 1 is prime. True False
b) Let a, b, c, and n be positive integers. If ab = ac mod n, then b = c mod n. True False
c) Let a, b, and c be positive integers. If a | c and b | c, then ab | c. True False