Chapter 2.8, Problem 8E

Use the alphabet $C$ from the preceding problem and the affine cipher with key $a=11\text{ and }b=7$ to decipher the message

$\text{R}\text{R}\text{R}\text{O}\text{A}\text{W}\text{F}\text{P}\text{H}\text{P}\text{W}\text{S}\text{U}\text{H}\text{I}\text{F}\text{O}\text{A}\text{Q}\text{X}\text{Z}\text{C}\text{:}\text{Q}\text{.}\text{Z}\text{I}\text{F}\text{L}\text{W}\text{/}\text{O}\text{:N}\text{X}\text{M}$ and state the inverse mapping that deciphers this ciphertext.

Exercise 7: Suppose the alphabet consists of $a$ through $z$, in natural order, followed by a colon, a period, and then a forward slash. Associate these "letters" with the numbers $0,1,2,...,28$, respectively, thus forming a $29$-letter alphabet, $C$. Use the affine cipher with key $a=3\text{ and }b=22$ to decipher the message

$\text{O}\text{V}\text{V}\text{J}\text{N}\text{T}\text{T}\text{B}\text{B}\text{B}\text{Q}\text{/}\text{F}\text{D}\text{L}\text{W}\text{L}\text{F}\text{Q}\text{/}\text{G}\text{A}\text{T}\text{Y}\text{S}\text{T}$ and state the inverse mapping that deciphers this ciphertext.