4. Recall that the order of an element a E Zp is the least natural number Tm = 1 mod p. (a) Compute the order of all the elements in Zis (b) Suppose Alice and Bob use Diffie-Hellman Key Exchange (DHKE) to share a secret key. However, due to a faulty setup, the a chosen in the DHKE setup has order 2. Show how an eavesdropper, Mallory, who copies the messages exchanged between Alice and Bob can compute the key shared between them. (c) Why or can never be p-1 in DHKE