Write python program for the Affine cipher with the following requirements:

$(1)$ Define a function to encrypt with the following header. It takes in an English message

$($containing $26$ letters only$)$ and a pair of keys $(a,b$ between $0$ and $25$ inclusively, with a as the

multiplicative key and $b$ as the additive key, and returns the ciphertext:

def encrypt$($message$,$ a$,$ b$)$:

$(2)$ Define a function to decrypt with the following header. It takes in a ciphertext and a pair of

keys $(a,b)$ between $0$ and $25$ inclusively, with a as the multiplicative key and b as the additive

key, and returns the ciphertext:

def decrypt$($message$,$ a$,$ b$)$:

$(3)$ Define a main$()$ function. First, it asks user what to do: encrypt or decrypt. Once the user

makes the choice, it then asks for the text and the keys. It should output the corresponding

results.

def main$()$: