Answer
The direction of the net electric field at P is in the negative y direction.
Work Step by Step
We can find write the general equation for the magnitude of an electric field:
$E = \frac{\vert q \vert}{4\pi ~\epsilon_0~r^2}$
Note that a magnetic field points toward a negative charge.
Since each charge is $-q$, which is a negative charge, each electric field is directed toward the charge producing it.
In part (d), we found that the x components of these two electric field vectors cancel.
In part (e), we found that the y components of these two electric field vectors add, and these y components both point in the negative y direction.
The direction of the net electric field at P is that of the adding components.
Therefore, the direction of the net electric field at P is in the negative y direction.
