Figure 8.8 shows the $P$ versus $V$ graphs of three expansions: (a) the reversible isothermal, (b) the irreversible isothermal, and (c) the reversible adiabatic. Plot the corresponding curves for $T$ versus $S$ of these three processes, letting all three processes start from the same initial point ( $T_1, S_1$ ) in the middle of your graph. Be quantitative if possible; otherwise, sketch an approximate curve. Label the curves $\mathrm{a}, \mathrm{b}$, and c . THINKING AHEAD $>[$ How should the areas under these curves compare?]