(b)
Given, $2ae = 16$ and $e = \sqrt{2}$
$\Rightarrow 2a\sqrt{2} = 16\ \Rightarrow a = 4\sqrt{2}$
$\because\ \ e = \sqrt{2},$ it means it is a rectangular hyperbola, where $a = b = 4\sqrt{2}$
$\therefore\ \$The equation of the hyperbola is $x^{2} - y^{2} = 32.$