Shelly, Susan, and Samantha are all working at an amusement park for the summer. The manager finds out that one of them left the key in the door to the security office. When he asked them who did it, they replied:

Shelly: Susan did it.
Susan: I didn’t do it.
Samantha: Susan did not do it.

The manager concluded that Susan did it because she was accused and was denying it.

Use an indirect proof to show that the manager was wrong and that Susan did not leave the key in the security office door.

Question

Shelly, Susan, and Samantha are all working at an amusement park for the summer.  The manager finds out that one of them left the key in the door to the security office.  When he asked them who did it, they replied:
 
Shelly: Susan did it.
Susan: I didn’t do it.
Samantha:  Susan did not do it.
 
The manager concluded that Susan did it because she was accused and was denying it.
 
Use an indirect proof to show that the manager was wrong and that Susan did not leave the key in the security office door.