Chapter 2.3, Problem 1P

Consider a tank used in certain hydrodynamic experiments. After one experiment the tank contains $150$ litter $\left(L\right)$ of a dye solution with a concentration of $3g/L$. To prepare for the next experiment, the tank is to be rinsed with fresh water flowing in at a rate of $3L/\min$, the well-stirred solution flowing out at the same rate. Find the time that will elapse before the concentration of dye in the tank reaches $2\%$ of its original value.