In a tank of capacity 400 liters, half filled with milk initially, one inlet pipe and one outlet pipe are operating. In the first hour, only the outlet pipe is operating and it takes out 20 liters of the mixture. In the next hour, the outlet pipe is closed and the inlet pipe pours in 30 liters of water. In the next hour the inlet pipe is closed and outlet pipe takes out 20 liters of the mixture and again in the next hour outlet pipe is closed and the inlet pipe pours in 30 liters of water. This process is repeated for another 4 hours. What is the approximate final quantity of water in the tank after 8 hours?
1) 105 liters
2) 149 liters
3) 91 liters
4) 141 liters