The following ciphertext has been obtained by Vigenere encryption.
ocwyikoooniwugpmxwktzdwgtssayjzwyemdlbnqaaavsuwdvbrflauplooubfgq
hgcscmgzlatoedcsdeidpbhtmuovpiekifpimfnoamvlpqfxejsmxmpgkccaykwfz
pyuavtelwhrhmwkbbvgtguvtefjlodfefkvpxsgrsorvgtajbsauhzrzalkwuow
hgedefnswmrciwcpaaavogpdnfpktdbalsisurlnpsjyeatcuceesohhdarkhwot
ikbroqrdfmzghgucebvgwcdqxgpbgqwlpbdaylooqdmuhbdqgmyweuik
(a) Use displacements of 5 and 6. Which displacement produces the largest number of coincidences?
(b) Find the key.
(c) Find the plaintext.
Note: You can use tools available on the internet, but you need to indicate them and how you used them. Or you can write your own programs.