A tank initially contains 150 lbm of a mixture that has equal mass concentrations of sodium sulfate and water. At t = 0, the inlet valve to the tank is opened, allowing a 15 lbm/min feed stream of 20 wt% sodium sulfate solution to enter. At the same time, the outlet valve to the tank is opened. The exiting solution has a flowrate of 15 lbm/min.

Assuming that the concentrations of the mixture inside the tank and exiting solution are the same, calculate the concentration of sodium sulfate in the tank after 10 minutes.