How to Stop Feedback

I have a quiz with 500 questions, random 40 show.  They were initially showing feedback and I imported them with feedback in the Quiz properties turned off but they are still showing feedback.  The main Quiz properties of points and attempts did overule the imported questions settings which I wanted, but the feedback setting didn't get cleared even though the main Quiz properties checkbox of Provide Feedback by Default was unchecked during the import.  Is there any way to clear the feedback for all the questions at the same time to set them to None?

Thanks,

Jo

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