Sample problem: Summing effects of several sources

Consider three point charges ($1\mu C$, $-1\mu C$, $1\mu C$) which lie at the vertices of an equilateral triangle (length of each side = 1cm).

1.

Make a 3D plot of the electric potential due to these charges, in the plane of the charges.

2.

Make a vector plot of the electric field, in the plane of the charges.

3.

Assuming that the triangle is centered at the origin, find the force on a test charge $q=-0.01\mu C$ placed at the origin.