Decrypt the following ciphertext which was generated using the

subsequently defined product cipher.

VDAAPARAYGYGFTCNQJCNQTRNVYCQFCGFQKVQNFCCQJTTGNXR

a$.$

The plaintext was firstly processed through an array based

transposition block cipher of length $24$ letters, with key $435162.$

b$.$

To the results of the first part apply a shift cipher with a key

corresponding to one less than that for the classical Caesar cipher.

You should add spaces back into the message as best you can.