Can someone just confirm if I'm doing these two problems correctly ... 1. How much energy is needed to place 4 positive charges, each of magnitude +5mC, at the vertices of a square of side 2.5cm 2. Choose one way of assembling the charges and calculate the potential at each empty vertex as this set of charges is assembled. For #1, I used the formula PE = kQQ/r PE = 9.0 x 106J and because there are 6 sets (4 sides and 2 diagonals) with similar lengths and charges, I added the PE values together, giving me a total of PET = 5.4 X 107J For #2, I'm not sure what exactly its asking me to do, but I used the formula V = kQ/r For the r, I used Pythagoreom Theorom to find the distance to the middle V = 2.55 x 109V and I'm not really sure, but there are 4 sets this time? So Total Potential = VA1+VA2+VA3+VA4?