A student conducts an experiment to determine the time constant \(\tau\) of an \(LR\) circuit consisting of an inductor of inductance \(L\) and a resistor of resistance \(R\). After a steady-state current \(I_0\) is established, the power source is removed at time \(t = 0\), and the current \(I(t)\) decays according to \(I(t) = I_0 e^{-t/\tau}\), where \(\tau = \dfrac{L}{R}\). To obtain a linear graph from the experimental data, which quantities should the student plot on the vertical and horizontal axes, and how is the time constant \(\tau\) determined from the slope \(m\) of the resulting best-fit line?