Modulus Function

Using the graph of \(y=|x^2-4|\), determine the number of intersections with the horizontal line \(y=k\) when:

1. \(k<0\);

2. \(k=0\);

3. \(0<k<4\);

4. \(k=4\);

5. \(k>4\).

Explain why the number changes at \(k=0\) and \(k=4\).