\textbf{189.} Inside a fixed-volume capsule, one mole of nitrogen gas is placed and the air pressure is $\frac{5}{4}$ of atmospheric pressure. If we add helium gas to the tank and keep the temperature constant, the pressure inside the tank becomes how many times atmospheric pressure? (Molar mass of nitrogen gas and helium are 28 g/mol and 4 g/mol respectively.)
\begin{itemize}
\item[(1)] $10$
\item[(2)] $9$
\item[(3)] $4$
\item[(4)] $2$
\end{itemize}