Consider the following way to encrypt a file. The encryption algorithm uses two n-byte arrays, A and B. The first n bytes are read from the file into A. Then A[0] is copied to B[i], A[1] is copied to B[ j], A[2] is copied to B[k], etc. After all n bytes are copied to the B array, that array is written to the output file and n more bytes are read into A. This procedure continues until the entire file has been encrypted. Note that here encryption is not being done by replacing characters with other ones, but by changing their order. How many keys have to be tried to exhaustively search the key space? Give an advantage of this scheme over a monoalphabetic substitution cipher.