4. Two rigid metal cylinders, both of volume 5.0 × 10−3 m3, contain gas. They are connected by a thin tube and a valve. Initially the valve is closed. The gas in cylinder A has pressure 1.5 × 105 Pa and temperature 10 ℃. The gas in cylinder B has pressure 2.0 × 105Pa and temperature 25.0 ℃.
The valve is opened and the gases mix. The final temperature of both cylinders is 18 ℃.
Calculate the final pressure of the gas in the cylinders. Give your answer in kPa.(3)