[tex]\displaystyle\bf\\20a^{3} b=-16\\\\\\a^{3} b=-\frac{16}{20} \\\\\\\boxed{a^{3} b=-\frac{4}{5} }\\\\\\a^{6} b^{2} =\big(a^{3} b\Big)^{2} =\Big(-\frac{4}{5} \Big)^{2} =\frac{16}{25} \\\\\\Otvet \ : \ B[/tex]