For an ideal gas, at constant volume (isochor), pressure \(P\) varies linearly with temperature \(T\): \[ P = \frac{nRT}{V} \] Slope of isochor in \(P\)-\(T\) graph is: \[ m = \frac{nR}{V} \] Given \(n\) and \(R\) constants, slope inversely proportional to volume \(V\).
Since \(V_1<V_2<V_3\), \[ m_1 = \frac{nR}{V_1}>m_2 = \frac{nR}{V_2}>m_3 = \frac{nR}{V_3} \]