Hi, i'm new here.. Can anyone help me with this tricky differential equations prob?

A tank contains 200 liter of fluid in which 30 g of salt is dissolved. Brine containing 1 g of salt per liter is then pumped into the tank at a rate of 4 liters per minute; the well mixed solution is pumped out at the same rate. Find the number of grams of salt A(t) in the tank at any time