Let \( a \in \mathbb{R} \) be such that the function
is continuous at \( x=0 \), where \( \{x\} = x - [ x ], \, [ x ] \) is the greatest integer less than or equal to \( x \). Then:
A box open from top is made from a rectangular sheet of dimension \( a \times b \) by cutting squares each of side \( x \) from each of the four corners and folding up the flaps. If the volume of the box is maximum, then \( x \) is equal to :
