Solve the all given parts of following question:

Question: Three objects are held in place on three corners of a square, with sides of length 1.55 m. The objects on two opposite diagonal corners of the square each have a charge of 6.24 µC. The object on the other corner of the square has a charge of -3.75 µC.

Part A: Find the electric potential at the fourth corner of the square.

Part B: If a fourth object, with a charge of 5.49 µC and a mass of 4.60 g, is placed at the fourth corner of the square and released from rest (while holding the other three objects in place), what will be the speed of the fourth object when it has moved an infinite distance away from its starting point?

I do not just need an answer, work and explanations/walkthrough would be much appreciated! Thanks.