Electric Field of a Disk

Two objects, whose charges are +3 nC and -2 nC, are separated by 1.0 mm. Find the magnitude of the attractive force that either charge exerts on the other.

In the figure below, L = 1.0 mm, q$_1$ = +3 nC, q$_2$ = -2 nC, and q$_3$ is +4 nC. Find the magnitude and direction of the net electrostatic force on q$_3$

Below are two charged spheres separated by a distance, X = 0.1 m from center to center. The sphere on the left carries a charge of 10 nC and has a radius 0.01 m. The sphere on the right carries a charge of -2 nC. Find the electric field at point A, which is 0.005 m from the center of the large sphere.

Given the 3 dimensional electric field, $\vec{E}$ = 200 $\frac{N}{C}$ $\hat{i}$ + 300 $\frac{N}{C}$ $\hat{j}$ + 400 $\frac{N}{C}$ $\hat{k}$ , and an area vector $\vec{A}$ = 0.2 m$^2$ $\hat{i}$ + 0.3 m$^2$ $\hat{j}$, find the electric flux. (this is a calculus based physics problem)