please don't solve if you are not sure.

Consider a large tank initially containing 101kg water. An inlet carries 1.9kg/min water into the chamber. Due to the age of the tank, there is small leak at the seams of the tank and the amount of water that leaks out depends on how much water is in the tank at any time. The leakage rate is estimated to equal 0.2*M(@t) kg/min, where M(@t) is the mass of the water in the tank at a time t. Set up the mass balance equation and solve it to find how much mass (in kg)of water is in the tank after 7 minutes? Margin of acceptable error is 5%