\[\left( 2ab^{3} \right)^{4}\ :\left( 2a^{2}b \right)^{2} =\]
\[= 2^{4}a^{4}b^{12}\ :2^{2}a^{4}b^{2} = 2^{2}b^{10} =\]
\[= 4b^{10}\]