A photosensitive metallic surface has work function, $hv_{\circ}$. If photons of energy $2hv_{\circ}$ fall on this surface, the electrons come out with a maximum velocity of $4 \times 10^6 \: m/s$. When the photon energy is increased to $5hv_{\circ}$, then maximum velocity of photoelectrons will be

Question

$\begin {array} {1 1} (a)\;2 \times 10^7\: m/s & \quad (b)\;2 \times 10^6\: m/s \\ (c)\;8 \times 10^6\: m/s & \quad (d)\;8 \times 10^5\: m/s \end {array}$