$\mathrm{E}_{\mathrm{y}}=-\frac{\delta \mathrm{V}}{\delta \mathrm{y}}=-4 \mathrm{\,Vm}^{-1}$

$a_{x}=\frac{q E_{1}}{m}=\frac{1 \times 10^{-6} \times 3}{0.1}$

$=-3 \times 10^{-5} \mathrm{\,ms}^{-2}$

$a_{y}=\frac{q E_{y}}{m}=\frac{1 \times 10^{-6} \times 4}{0.1}$

$=-4 \times 10^{-5} \mathrm{\,ms}^{-2}$

Time taken to cross the $X$ - axis

Using $s=u t+\frac{1}{2} a t^{2}$

$3.2=\frac{1}{2} \times 4 \times 10^{-5} \times t^{2}$

$t=400 \mathrm{\,s}$