A hydraulic brake system uses an incompressible fluid to transmit force from a master cylinder to two identical wheel cylinders. The piston in the master cylinder has diameter \(d\), and an input force of magnitude \(F\) is applied to it. The fluid line branches equally to the two wheel cylinders, each containing a piston of diameter \(D\). Assuming the system is static and friction is negligible, which of the following expressions represents the total magnitude of the force exerted by the two wheel cylinder pistons combined?