Error trying to use Fragment

I am new to Android.  I have been working thru some examples in a book called  Head First Android Development.  I entered a small program using fragments and get a Casting Error.

cannot cast andoid.app.fragment to com.hilights.rsobol.workout.WorkoutDetailFragment

I am hoping someone can download the attached zip file and show me the error of my ways. It is most likely a simple error that someone with some experience can see.

Thank you in advance for your help,

Rob

rsobol@hilightsinc.com

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Created by Michael Levin Dec 18, 2008 at 6:56pm. Last updated by Michael Levin May 4, 2018.

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