In: Advanced Math
A tank initially contains 10 liters of clean water (with no salt in it). Every minute, a solution containing one liter of water and one gram of salt is added to the tank, and two liters of fluid are drained from the tank. The fluid in the tank is mixed continuously so that the salt is distributed evenly throughout the water in the tank. How many minutes does it take for the tank to contain 2 grams of salt?