1) If the two most common letters in a long ciphertext, encrypted by an affine transformation C ≡ aP+ b (mod 26), are X and Q, respectively, then what are the most likely values for a and b?
2) Find the product cipher obtained by using the transformation C ≡ aP+ b (mod 26) followed by the transformation C ≡ cP+ d (mod 26), where (a, 26) = (c, 26) = 1.