The following is my c++ task. Please keep basic constructs as we are not allowed to use constructs not learned in class. We have learned functions and loops of course. But We have not learned classes structure maps etc.

While the above image has the question I am also sending the introduction if u need it.

Task C. Implementing Vigenere cipher encryption Add the following function to your program to implement a Vigenere Cipher: string encryptvigenere (string plaintext, string keyword); You may assume that the keyword contains only lowercase alphabetic characters a z Your main program should demonstrate that this function works and you should also include doctest tests for this function. Example: s ./vigenere Enter plaintext: Hello, World! Enter keyword : cake ciphertext Jevpq, Wyvnd