Answer
$E = 0.023~N/C$
Work Step by Step
We can find the electric field strength:
$v_d = \frac{e~\tau~E}{m}$
$E = \frac{v_d~m}{e~\tau}$
$E = \frac{(2.0\times 10^{-4}~m/s)(9.1\times 10^{-31}~kg)}{(1.6\times 10^{-19}~C)(5.0\times 10^{-14}~s)}$
$E = 0.023~N/C$
