To estimate the price of the 2018 Changan CS75 I4 1.8L Turbocharged Plus Smart (Mid) with 112500 km mileage, I considered several data points. First, I looked at the selling prices of similar cars. The closest match is a 2017 Changan CS75 I4 1.8L with 131000 km, Plus Smart (Mid) variant, sold for 21500 SAR on 2023-10-26. Another relevant data point is a 2020 Changan CS75 I4 1.8L Turbocharged Plus Smart (Mid) with 86000 km, sold for 39000 SAR on 2023-11-21. Given the mileage and year differences, I adjusted the price downward. Additionally, a 2018 Changan CS75 I4 1.8L Turbocharged Plus Smart (Mid) with 112500 km is listed for 31500 SAR, but listed prices are generally higher than selling prices. Considering these factors, I estimated the market price accordingly.