A large tank of unknown total volume is initially filled with 6000 g of a 10% by mass sodium sulfate solution. Into this tank a 50% sodium sulfate solution is added at a rate of 40 g/min. At the single outlet to the tank flows a 20 g/L solution at a rate of 0.01667 L/sec. Please calculate 

(a) The total mass in the tank after 2 h and 

(b) The amount of sodium sulfate in the tank after 2 h.