A brine solution of salt flows at a constant rate of 4 L/min into a large tank that initially held 100L of water. The solution inside the tank is well stirred and flows out of the tank at a rate of 3 L/min. If the concentration of salt in the brine entering the tank is 0.2 kg/L, determine the mass of salt in the tank after t minutes. When will the concentration of salt in the tank reach 0.1 kg/L?

let S = salt, I come up with dS/dt + 3S/100+t = .8 and get an integrating factor of (100+t)^3 and come up with S = .2(100+t) + C(100+t)^3 but now I\'m stuck. What do I do?\n