How do I get the plunger?

Hint 1 of 8:

The Robot Maker won't let you take the plunger.

Hint 2 of 8:

You need to "off" the Robot Maker.

Hint 3 of 8:

Talk to him and ask him questions.

Hint 4 of 8:

He says that there is not a question he cannot answer.

Hint 5 of 8:

Maybe if you could find a question that he couldn't answer, his circuits
might fry.

Hint 6 of 8:

Have you heard anything about unsolvable questions?

Hint 7 of 8:

Ms. Fit is reading a book of unsolvable questions.  You need to use this book
on the Robot Maker.