Work From Electric Force

Practice: An electron moves from point A to point B. The potential difference between these two points is 100 V. What is 

a. the point of higher potential?
b. the work done on the electron?
c. the final speed of the electron if its initial speed is zero?

Practice: What work is needed to assemble an equilateral triangle of side length 5 cm, with a 5µC charge at each vertex?