IN C language

I need Question 13 to be done but it required the previous questions 12 in order to do 13

2. Write a program to help an analyst decrypt a simple substitution cipher. Your program should take the ciphertext as input, compute letter frequency counts, and display these for the analyst. The program should then allow the analyst to guess a key and display the results of the corresponding "decryption" with the putative key. 3. Extend the program described in Problem 12 so that it initially tries to decrypt the message. One sensible way to proceed is to use the computed letter frequencies and the known frequencies of English for an initial guess at the key. Then from the resulting putative decryption, count the number of dictionary words that appear and use this as a score. Next, for each letter in the key, try swapping it with the letter that is adjacent (with respect to frequency counts) and recompute the score. If the score improves, update the key; if not, don't change the putative key. Iterate this process until the score does not improve for an entire pass through the alphabet. At this point you will give your putative decryption to the analyst. To aid the analyst in the manual phase, your program must maintain all of the functionality of the program in Problem 12