before it becomes empty. set up the problem

3. A tank has a volume of 50 liters. It initially contains 30 liters of brine (salt solution) with a concentration of 0.2 kg per liter. Brine with a concentration of 0.3 kg per liter begins to flow into the tan at a rate of 4 liters per minute. The thoroughly mixed solution escapes through a leak at the rate of 6 liter per minute. Set up an initial value problem for finding the amount of salt in the tank before it becomes