A fish tank initially contains 40 liters of pure water. Brine of constant, but unknown, concentration of salt is flowing in at 6 liters per minute. The solution is mixed well and drained at 6 liters per minute. a. Let æ be the amount of salt, in grams, in the fish tank after t minutes have elapsed. Find a formula for the rate of change in the amount of salt, dæ/dt, in terms of the amount of salt in the solution x and the unknown concentration of incoming brine c. dæ grams/minute dt b. Find a formula for the amount of salt, in grams, after t minutes have elapsed. Your answer should be in terms of c and t. æ(t) grams c. In 35 minutes there are 25 grams of salt in the fish tank. What is the concentration of salt in the incoming brine? g/L %3=