We will consider Diffie−$-$Hellman key exchange. Alice and Bob have agreed to use the one−$-$way function x 9$9$x ($($mod 17)which they will use to set up a key which only they know. Alice chooses the secret number 5,$\mathrm{}$ and Bobs secret number is 7$.$ Use the rules of modular arithmetic to compute the key from this data, showing your working.