You meet four people, A, B, C, and D. One of them is a knight, one is a liar, one is a knave, and one is a normal who tells the truth and lies at random. They make the following statements.
A:I am a liar.
A:C is a normal.
B:D is a knight.
C:B is a knave.
What are A, B, C, and D?