What is wrong with this line of code?

$answer_count = count($question['Answer']);

I am trying to start learning cakePHP using the book CakePHP
Application Development. I keep getting this error though that points
to this line:

Undefined index: Answer [APP\views\questions\home.ctp, line 10]

In home.ctp, I need to display the number of "Answer" posts. Similar
to Comments for blog posts, but this is Answers for question posts.
Example in the book...but anyways. What is wrong?

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