Consider a thin slice of the first rod, of thickness dx1, that is located a distance x1 from the origin and a thin slice of the second rod, of thickness dx2, that is located a distance x2 from the origin. Enter an expression for the magnitude of the force dF12 that the thin slice of rod 1 exerts on the thin slice of rod 2, in terms of L1, L2, Q1, Q2, x1, x2, and the Coulomb constant k.