Its kind of hard to tell what the book is looking for with-out knowing what you should know at this point in the book and what you've been taught so far.

With that said it appears you need will need 2 classes for the shapes

This is just pseudo code

Code:

Class Sphere
Int Diameter
Function Int Volume()
Return 1.25 * Pi * (Diameter ^ 3)
End Function
Function Int Area()
Return 4 * Pi * (Diameter ^ 2)
End Function
Sub Override ToString()
Return "I am an object with a height of %1, width of %2 and length of %3"
End Function
End Class
Class Square
Int Length
Int Width
Int Height
Function Int Volume()
Return Length * Width * Height
End Function
Function Int Area()
Return Length * Width
End Function
Sub Override ToString()
Return "I am an object with a height of %1, width of %2 and length of %3"
End Function
End Class

Hopefully this point you in the right direction, someone else may jump in and help more, but i gotta bounce, i'll check back later tonight(maybe)