In the system shown, two copper rods AB and CD with a diameter of 15 mm are fixed to a wall and a rigid plate, along with a steel rod EF with a diameter of 20 mm. Given that the horizontal displacement at point F of rod EF is 0.75 mm under the loading condition shown, determine the magnitude of the force P. Take Ecopper = 100 GPa, Esteel =210 GPa