Hey guys, can you help me with this problem?

A tank initially contains 120 liters of pure water. A mixture containing a concentration of x g/liter of salt enters the tank at a rate of 2 liters/min, and the well-stirred mixture is allowed to leave the tank at the same rate. Find an expression in terms of x for the amount of salt in the tank at any time t. Also find the limiting amount of salt in the tank as t-->infinity

Thanks guys