a) Write a C++ function that inputs a text message and a positive integer k less than 26 and outputs an encrypted version of the message using the shift cipher with key k. b) Write a C++ function that...

Answer a part.

Extracted text: a) Write a C++ function that inputs a text message and a positive integer k less than 26 and outputs an encrypted version of the message using the shift cipher with key k. b) Write a C++ function that inputs a positive integer k less than 26 and a text message encrypted using the shift cipher with key k and outputs a decrypted version of the message. c) Write a C++ program to test your functions from parts a) and b).