To estimate the price of the 2018 Nissan X-Trail I4 2.5L S 2WD (5-Seater) (Base) with 240000 km mileage in average condition, I considered the following data points: 1. A similar car with 228000 km mileage, same variant, and condition sold for 45000 SAR on 2024-09-01. 2. Another similar car with 135000 km mileage, same variant, and condition sold for 40000 SAR on 2024-01-13. 3. A similar car with 217000 km mileage, different variant (S AWD), and condition sold for 41500 SAR on 2024-08-31. 4. The listed prices for similar cars with 240000 km and 228000 km mileage are 46500 SAR and 47500 SAR respectively. Given the higher mileage of the target car (240000 km) compared to the sold cars, I adjusted the price downwards. The most relevant data point is the car sold for 45000 SAR with 228000 km, which is very close in mileage and variant. Considering the additional 12000 km on the target car, I estimated a slightly lower price.