cryptography/security engineering

Recall that the key-length of DES is 64 bits, however, 8 bits of it is for error checking (parity bits). So only 56 bits of the key are independent. By what factor is the key-space size of AES with a 256 bit key bigger? Select one: a. 8 b. 256 c. 2 d. about 200 e. 256 f. 100000000 g. 200 h. 256