$\,\quad\quad\quad\quad2s\quad\quad\quad3s$
$k _{ sp } =(2 s )^{2}(3 s )^{3}$
$=4 s ^{2} \times 27( s )^{3}$
$=108( s )^{5}$
$( s )^{5} =\frac{1.08 \times 10^{-73}}{108}$
$\Rightarrow s =10^{-15}$
[અહીં $K_b\,(NH_4OH) = 10^{-5}$ અને $log\,2 = 0.301$ ]
$(K_w = 10^{-14})$