The pressure inside two gas cylinders of volume $$25\ \text{m}^3$$ and $$50\ \text{m}^3$$ are 10 kPa and 20 kPa respectively. The cylinders are kept at the same temperature and separated by a valve. What is the pressure in the combined system when the valve is opened?

A

30 kPa

B

15 kPa

C

16.7 kPa

D

2.5 kPa