11. (a) Use the Euclidean Algorithm to determine the greatest common divisor of 28 and 52. (5 marks) (b) The context for this question is RSA key generation. Two prime numbers are chosen, p = 37 and q = 41. Which of the following prime numbers 5, 7, 11 can be used as valid encryption key, e? Show your reasoning. (6 marks) (c) Alice and Bob agree to communicate using the RSA cryptosystem. Alice has a private key (n = 1739, d = 55) and a public key (n = 1739, e = 523). Alice receives the cyphertext C = 2 from Bob. Decrypt this message