Shown to the right are three charges arranged at the corners of a rectangle. [20 points ] a. Calculate the potential at the bottom-right corner (marked with an X) due to the -3.0nC charge. [3 points] b. Calculate the potential at the bottom-right corner due to the +3.0nC charge. [3 points] c. If the total potential at the bottom-right corner is +1050V, what is the unknown charge (sign and size) at the top-left corner? [6 points] d. A proton was placed at the X and allowed to shoot away from the rectangle. Write a few sentences to describe the physics principles and ideas you would need to use to calculate the speed of the proton very far from the rectangle. [4 points] e. Calculate the proton's speed (the proton's mass is 1.6710-27kg). +3.0 nC q 2.0 cm -3.0 nC 4.0 cm