From a Rectangular Piece of Cardboard Having Dimensions W = $( 0,9 )$

Multiple Choice

From a rectangular piece of cardboard having dimensions W = 18 and L = 40 an open box is to be made by cutting out identical squares of area x ² from each corner and turning up the sides (see Illustration) . Find all positive values of x such that the volume of the box V ( x ) > 0. Include only allowable values of x in your answer.

A) $( 0,9 )$
B) $( 0,9 ) \cup ( 20 , \infty )$
C) $( 0,20 )$
D) $( - \infty , 9 ) \cup ( 20 , \infty )$
E) $( 0 , \infty )$