Hi, I have a maple project and one of the questions reads: 

a. | Initially, a 100 – liter tank contains a salt solution with concentration 0.5 kg/liter. A fresher solution with concentration 0.1 kg/liter flows into the tank at the rate of 4 liter/min. The contents of the tank are kept well stirred, and the mixture flows out at the same rate it flows in.
i. Find the amount of salt in the tank as a function of time.

ii. Determine the concentration of salt in the tank at any time.