Alice and Bob are using the Diffie-Hellman algorithm for public-key sharing. They agree to use the prime number p = 19 and generator g = 2. Alice think of a secret number a and announce the number gmod(p) which is 4. Bob think of a secret number band announce the number g mod(p) which is 16. Alice and Bob can now each compute gabmod(p) and use this number as a shared secret key. Break the code and determine the secret key. The answer should be a number from the set {1,2,3,...,18)