If no radiation is falling on plate C, the number of electrons appeared on the surface of cathode C when jockey is connected at end P of the rheostat is

Question

$\begin {array} {1 1} (a)\;8.85 \times 10^6 & \quad (b)\;8.85 \times 10^9 \\ (c)\;1.77 \times 10^{10} & \quad (d)\;0 \end {array}$