A student performs an experiment to determine the universal gas constant \(R\) using a sample containing a known amount \(n\) of an ideal gas. The student collects data for the pressure \(P\), volume \(V\), and temperature in degrees Celsius \(T_C\) across several trials in which both pressure and volume are varied. Which of the following describes the quantities that should be plotted on the vertical and horizontal axes to produce a linear graph, and the correct expression for the universal gas constant \(R\) in terms of the slope \(m\) of the line?