As shown below, three point charges $($the charge for each is shown in terms of Q$)$ are each a distance $L$ away from point $P.$ Determine the potential at point $P.$ Express your answer in terms of $k,Q,$&$L.$

$=$

Part B: Rectangle

Three point charges $($the charge for each is shown in terms of Q$)$ are arranged at the corners of a rectangle as shown in the figure below. What is the potential at the fourth corner $($point P$)?$ Express your answer in terms of k$,$ Q$,$ & L$.$

$=$