A tank initially contains 100 liters of salt water with 1 kilogram of dissolved salt. A well mixed salt water solution containing 4 kilograms of salt per 100 liters is pumped into the tank at a rate of 10 liters per minute. The salt water in the tank is kept thoroughly mixed and is drained at a rate of 5 liters per minute. Set up an initial value problem that represents the rate of change in the amount of salt (in kilograms) in the tank at time t (in minutes). O dy 4 y dt 10 5t + 100 : 3(0) = 1 O dy y dt t + 20 ' 3(0) = 100 O dy y = 4- dt 5t + 100 ' 3(0) = 100 O dy 4 dt 100 5y , y(0) = 1 O dy y dt t + 20 : y(0) = 1