a) Show whether 18 and 25 are relatively prime using the Euclidean algorithm b) Find two integers x and y such that 18x + 25y = 1 (You can use your solution for part a) c) Consider the number 451 (= 18.25 + 1). Explain why any prime number that divides 451 cannot be a divisor of either 18 or 25. d) Find an integer z such that z = 7 (mod 18) and z = 13 (mod 25). You may find the answer to part (b) useful. You may express your answer as an arithmetic expression without evaluating it