Two massless rods are attached to frictionless pivots, with their ends touching. The distances between the pivot points and the endpoints of the rods are shown in the figure. Neglect friction force between the rods, if a force $\mathrm{F}=9\mathrm{N}$ is applied at the left end of the left rod, what force F₁ (in newton) must be applied at the right end of the right rod to keep the system in equilibrium.