A pipe can empty $\left(\frac{5}{6}\right)^{th}$ part of a cistern in 20 minutes. The part of cistern which will be empty in 9 minutes is :

$\frac{3}{5}$ $\frac{3}{8}$ $\frac{4}{5}$ $\frac{5}{9}$

$\frac{3}{5}$