$(1$ point$)$ A cryptography student has accidentally used the same keystream to encrypt two different messages, $M_1$ and $M_2.$ We know that the

ciphertexts are $C_1=0xb1dcb1e81bb933ee$ and $C_2=0xa36da13ab52d8552.$ We also happen to know that

$M_1=0xe7cb99c00c599b7e.$

a$)$ What is $M_2$ in hexadecimal? Please give your answer a leading $0x$ and use lowercase letters only.

b$)$ What is the keystream? Please give your answer a leading $0x$ and use lowercase letters only.

Hint: These are all $8$ byte numbers and will fit in an unsigned long type on most systems.