$(1$ point$)$ Alice and Bob are using the ElGamal cipher with the parameters $p=157$ and $=5.$

Suppose Alice is observed sending public ephemeral key $k_E=40$ and Bob sends public key $=145.$

Their private keys are $i=112$ and $d=130,$ respectively.

a$)$ What is the masking key $k_M?$

b$)$ What is the encryption of $x=31?$