The secret code of a group of students is a three-digit number with distinct non-zero digits. Discover the code using the following information.

$\begin{array}{llll}1 & 2 & 3 & \text { No digit is correct. }\end{array}$

$4 \quad 5 \quad 6 \quad$ Only one digit is correct and in the right position.

$\begin{array}{llll}6 & 1 & 2 & \text { Only one digit is correct, but in the wrong position. }\end{array}$

$\begin{array}{llll}5 & 4 & 7 & \text { Only one digit is correct, but in the wrong position. }\end{array}$

$8 \quad 4 \quad 3$ Only one digit is correct and in the right position.
(a) 137
(b) 876
(c) 768
(d) 678
(e) 576
The correct option is (b).

The code can only be formed with the digits 1, 2, 3, 4, 5, 6, 7, 8, and 9.

From the first piece of information, we know that 1, 2, and 3 are not part of the code (numbers that are not part of the code are underlined in the tables). From the third piece of information, we conclude that 6 is part of the code, and its position is - 6 - ${ }_{---}$ or 6.

From the second piece of information, it follows that 4 and 5 are not part of the code, and the position of 6 in the code is $\qquad$ 6. From the last piece of information, we only have that the code is of the form 8 6. With the fourth piece of information, we complete the code: 876. $\qquad$

| $\underline{1}$ | $\underline{2}$ | $\underline{3}$ |
| :---: | :---: | :---: |
| 4 | 5 | $\mathbf{6}$ |
| $\mathbf{6}$ | $\underline{1}$ | $\underline{2}$ |
| 5 | 4 | 7 |
| 8 | 4 | $\underline{3}$ |


| $\underline{1}$ | $\underline{2}$ | $\underline{3}$ |
| :---: | :---: | :---: |
| $\underline{4}$ | $\underline{5}$ | 6 |
| 6 | $\underline{1}$ | $\underline{2}$ |
| $\underline{5}$ | $\underline{4}$ | 7 |
| 8 | $\underline{4}$ | $\underline{3}$ |