Alice wants to send a message to Bob in secure way.
Alice encrypted a plaintext PA = ¡°IMISSYOU¡± = 0x494D495353594F55 by using DES and obtained ciphertext CA = 0xFA26ED1833264435.
Alice sent the ciphertext CA and the secret key to Bob. The secret key was encrypted by converting each of its letters to a pair of digits giving its position in the typewriter keyboard. More precisely, the following table is used.

1 2 3 4 5 6 7 8 9 0
1 Q W E R T Y U I O P
2 A S D F G H J K L
3 Z X C V B N M

In this manner, 'A' is converted to 21, 'B' to 35, etc. In transmission, all of the first digits were lost and the received secret key resulted in the pairs:

?8  ?9  ?9  ?4  ?3  ?5  ?9  ?5

After a few minutes, Bob recovered the secret key and smiled. Bob decided to reply in the same way.
Bob encrypts a plaintext PB = 0xB6B2B6ACACA6B0AA by using DES and obtained ciphertext CB = 0x05D912E7CCD9BBCA.
What is the secret key which Bob used? (0x????????????????) (Bob¡¯s secret key is different from Alice¡¯s secret key)

Answer: strupr(????????????????)