Argon gas with k = 1.667, c_p = 0.5203 kJ/kg·K, and R = 0.2081 kJ/kg·K enters an 8-cmdiameter adiabatic duct with V₁ = 70 m/s, T₁ = 520 K, and P₁ = 350 kPa. Taking the average friction factor to be 0.005 and letting the exit temperature T₂ vary from 540 K to 400 K, evaluate the entropy change at intervals of 10 K, and plot the Fanno line on a T-s diagram.