168- The ($P-V$) diagram of a perfect gas that goes from state i to state f via three paths a, b, and c, according to the figure below. If the internal energy change of the gas is $\Delta u$ and the heat absorbed by the gas is $Q$, which relation is correct? \begin{minipage}{0.35\textwidth} [Figure: P-V diagram showing three paths a, b, c from state i to state f, with P on vertical axis and V on horizontal axis] \end{minipage} \begin{minipage}{0.6\textwidth} (1) $Q_c > Q_b > Q_a > \circ$ (2) $Q_a > Q_b > Q_c > \circ$ (3) $\Delta u_a = \Delta u_b = \Delta u_c < \circ$ (4) $\Delta u_a = \Delta u_b = \Delta u_c = \circ$ \end{minipage}
\textbf{168-} The ($P-V$) diagram of a perfect gas that goes from state \textbf{i} to state \textbf{f} via three paths \textbf{a}, \textbf{b}, and \textbf{c}, according to the figure below. If the internal energy change of the gas is $\Delta u$ and the heat absorbed by the gas is $Q$, which relation is correct?
\begin{minipage}{0.35\textwidth}
\textit{[Figure: P-V diagram showing three paths a, b, c from state i to state f, with P on vertical axis and V on horizontal axis]}
\end{minipage}
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\begin{minipage}{0.6\textwidth}
(1) $Q_c > Q_b > Q_a > \circ$
(2) $Q_a > Q_b > Q_c > \circ$
(3) $\Delta u_a = \Delta u_b = \Delta u_c < \circ$
(4) $\Delta u_a = \Delta u_b = \Delta u_c = \circ$
\end{minipage}