Two insulated tanks A and B are connected by a valve. Tank A has a volume of 30 ft3 and initially contains argon at 50 lbf/in 2, 50 F. Tank B has a volume of 60 ft3 and initially contains ethane at 30 lbf/in2, 120 F. The valve is opened and remains open until the resulting gas mixture comes to a uniform state. Find the final pressure and temperature and the entropy change for the process.