A Slip in the Logbook

Very Hard — logic-grid deduction puzzle

After three smooth carrying tests, the judges found one wrong line in the logbook.

It was August 2026 at the arena in the capital, and the humanoid robot games had reached the carrying tests. In the practice hall, the last three tests of the day ran one after another. Each test had its own engineer, its own robot, its own kind of cargo and its own number of pieces delivered. One robot even bowed to its empty trolley after unloading it, and the crowd gave it a little round of applause. Then the judges opened the logbook and frowned: one of the lettered lines was wrong. Every other clue can be trusted.

Clues

1. Logbook line A: The robot in the second test delivered 6 pieces.
2. Logbook line B: If the clips delivery was not 32 pieces, then Ning was the engineer for it.
3. Logbook line C: Only one of two things was true of the third test: its robot was Doudou, or its robot delivered 32 pieces.
4. Only one of logbook lines A, B and C was false; the other two were true.
5. The robot with the bolts delivered fewer pieces than the robot with the washers.
6. Rui's test ran right before or right after the test with Tuantuan.
7. The first test, Jia's test and the test with the bolts were three different tests.
8. Of the following, exactly two were true and one was false: Tuantuan carried the bolts; the first test was Jia's; Jia's cargo was the clips.
9. Only one of these was true, and the other two were not: Rui's robot delivered 39 pieces; Doudou carried the washers; the bolts were carried in the first test.

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