The maximum number of isomers (including stereoisomers) that are possible on monochlorination of the following compound is
\begin{matrix} &\underset{|}{CH_3}\\& \underset{\diagup \ \ | \ \ \diagdown }{C} \\ & CH_3CH_2 \ \ \ \ H \ \ \ CH_2CH_3 \end{matrix}\begin{matrix} & &\quad \quad \quad \quad CH_3 & \\ & & \quad \quad \quad \quad| & \\ & & CH_3CH_2C\ast & – & CH_2CH_2Cl \\ & & \quad \quad \quad \quad | & & &\\ & &\quad \quad \quad \quad H& & & \\\end{matrix}
\begin{matrix} & &\quad \quad \quad \quad CH_3 & \\ & & \quad \quad \quad \quad| & \\ & & CH_3CH_2C\ast & – & CHCH_3 \\ & & \quad \quad \quad \quad | & & &\\ & &\quad \quad \quad \quad H& & & \\\end{matrix}
\begin{matrix} & &\quad \quad \quad \quad CH_3 & \\ & & \quad \quad \quad \quad| & \\ & & CH_3CH_2C & – & CH_2CH_3 \\ & & \quad \quad \quad \quad | & & &\\ & &\quad \quad \quad \quad Cl& & & \\\end{matrix}
\begin{matrix} & &\quad \quad \quad \quad CH_2Cl& \\ & & \quad \quad \quad \quad| & \\ & & CH_3CH_2C & – & CH_2CH_3 \\ & & \quad \quad \quad \quad | & & &\\ & &\quad \quad \quad \quad H& & & \\\end{matrix}