The orginal method is there as is... I didn't modify it. I simply added another method.
Additionally based on the comment at the top of the file...

// TODO: this class should probably be called "PageArea" or something like that

it seemed to me that Page.java is the place where all area calculations should be housed and hence I decided the add that method.

I can anyways move the calculations out of Page.java... but just want a quick confirmation from you again if possible please.