Which of the following sources is not currently use to produce electricity for us in our homes a. coal b. oil c. nuclear d. lunar i’ve tried to go back in my text book but couldn’t find anything on it

Four point charges each having charge q are located at the corners of a square having sides of length a. find symbolic expressions for the following. (a) the total electric potential at the center of the square due to the four charges (use any variable or symbol stated above along with the following as necessary: ke.) vtotal= (b) the work required to bring a fifth charge p from infinity to the center of the square (use any variable or symbol stated above along with the following as necessary: w=