The correlation coefficient of two variables $x$ and $y$ is 0.8. The regression coefficient of $y$ on $x$ is 0.2 then the regression coefficient of $x$ and $y$ is

Question

$\begin {array} {1 1} (A)\;3.2 & \quad (B)\;-3.2 \\ (C)\;4 & \quad (D)\;0.16 \end {array}$