Farm Machinery

In an electrostatic induction spray nozzle, spray liquid flows at rate $\dot{m} = 0.002\text{ kg/s}$ and charging electrode induces a net spray current $I = 4.0\text{ \mu A}$ ($4.0 \times 10^{-6}\text{ C/s}$). The charge-to-mass ratio $q/m = I / \dot{m} = \frac{4.0 \times 10^{-6}}{0.002}$ in $\text{mC/kg}$ is: