a$.$ Which parameters and design choices determine the actual algorithm of a Feistel cipher?

b$.$ Consider a Feistel cipher composed of $16$ rounds with block length $128$ bits and key length $128$ bits. Suppose that for a given key K$,$ the key scheduling algorithm determines values for the first $8$ round keys, k$1,$ k$2,$ k$8$ and then sets k$9=$k$8,$ k$10=$k$7,$ kll$=$k$6,....$ k$16=$k$1....$ Suppose that you have a ciphertext C$.$ Explain how, with access to an encryption oracle, you car decrypt and determine using just a single oracle query. This shows that such a cipher is vulnerable to a chosen plaintext attack. $($An encryption oracle can be thought of as a device that, when given plaintext, returns the corresponding ciphertext. The internal details of the device are not known to you and you cannot break open the device. You can only gain information from the oracle by making qucries to it and observing its responses.$)$ Show that DES decryption is the inverse of DES encryption