An affine cipher is a version of a mono-alphabetic substitution cipher, in which the letters of an alphabet of size m are first map to the integers in the range 0 to m-1. Subsequently, the integer representing each plain text letter is transformed to an integer representing the corresponding cipher text letter. The encryption function for a single letter is E(x) = (ax + b) mod m, where m is the size of the alphabet and a and b are the key of the cipher, and are co-prime. Trudy finds out that Bob generated a cipher text using an affine cipher. She gets a copy of the cipher text, and finds out that the most frequent letter of the cipher text is ’R’, and the second most frequent letter of the cipher text is ’K’. Show how Trudy can break the code and retrieve the plain text.