\textbf{9.} A quantity of an element exists. If each hour $\dfrac{1}{9}$ of the mass is lost, after how many minutes will $\dfrac{1}{6}$ of the element's mass remain? $\left(\log_2^5 = 1/4 \text{ and } \log_3^5 = 2/4\right)$
\medskip
(1) $380$ \hfill (2) $360$ \hfill (3) $440$ \hfill (4) $420$
\bigskip