$(1$ 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

$C_1=0xd51093d2ca5d8da8$ and $C_2=0xa5d94a7610741b1c.$ We also happen to know that

$M_1=0x5$ fece$20799963719.$

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 $0$x and use lowercase letters only.

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