Two identical point particles, each with positive charge \(+Q\), are fixed on the \(x\)-axis at positions \(x = -d\) and \(x = +d\). A third point particle with positive charge \(+q\) is constrained to move along the \(y\)-axis and is placed at position \((0, y)\). Which of the following graphs best represents the total electric potential energy \(U_{\text{sys}}\) of the three-charge system as a function of the position \(y\)?