85. 

Suppose the prosecutor from problem 83 made the following two statements in court:

1) Either $X$ is not guilty, or $Y$ is guilty.
2) $X$ is guilty.

What conclusion would you draw based on these statements?
85. Suppose the accuser were a liar. Then statement (1) is false, so $\mathrm{X}$ is guilty and Y is not guilty. Therefore, X is guilty. But statement (2) is also false, so $\mathrm{X}$ is not guilty, and we arrive at a contradiction. Thus, in this problem, as in the previous one, the accuser is a knight. Then, by statement (2), X is guilty. From statement (1) (since $\mathrm{X}$ is not innocent), we conclude that Y is guilty. Therefore, in this case, both X and Y are guilty.