Answer
$2.0\times 10^{15}$ electrons per second hit the screen.
Work Step by Step
We can find the number of electrons per second:
$\frac{320\times 10^{-6}~C/s}{1.6\times10^{-19}~C} = 2.0\times 10^{15}~s^{-1}$
$2.0\times 10^{15}$ electrons per second hit the screen.
