In a large mixing tank, 40 kg of salt was dissolved in 300 L of water. Different brine with a salt concentration at a volumetric flow rate of 5 L/da into the tank is fed. On the other hand, a pump operating at a volumetric flow of 8 L/da drains the salt water out. The tank is well mixed and fed into the tank. Since the salt concentration of the flux is 6 kg/L: a. It gives the change in the amount of salt in the tank over time before the tank is empty. derive the expression. b. 5 minutes before the tank is empty, the amount of salt in the tank and Calculate the concentration. [Assume all densities are equal. All your calculation steps show.] urgent please