An infinity long solid cylinder of radius R has a uniform volume charge density $\rho$. It has a spherical cavity of radius $\frac{R}{2}$ with its centre on the axis of the cylinder, as shown in the figure. The magnitude of the electric field at the point P, which is at a distance $2R$ from the axis of the cylinder, is given by the expression $\frac{m\rho R}{n{\epsilon }_{{ }_o}}$. The value of  $(m\times n)$ is