Suppose the DES encryption is denoted by $C=E_K[P],$ while the DES decryption is denoted by $P=D_K[C],$ where $C$ and $P$ refer to the ciphertext and the plaintext, respectively. Which of the following expression denotes the encryption and decryption of the $3$DES algorithm? $(K_1,K_2,$ and $K_3$ are secret keys$).$