In an experiment to determine the vacuum permeability \(\mu_0\), two long, parallel, flexible wires carrying equal steady currents \(I_0\) in the same direction are held at a separation distance \(d\). A force sensor measures the magnetic force per unit length, \(F/\ell\), between the wires for various values of \(d\). In order to yield a linear graph whose slope \(m\) can be used to determine \(\mu_0\), which quantities should be plotted on the vertical and horizontal axes, and what is the correct expression for \(\mu_0\) in terms of the slope \(m\) and given quantities?