Two tanks (each can hold 100 gallons) are interconnected. Tank 1 originally has 30 gallons of water and 2 lbs of salt. Tank 2 originally has 40 gallons of water and 5 lbs of salt. Water having 1 lb of salt per gallon flows into Tank 1 at the rate of 2 gallons per minute. Solution flows from Tank 1 in Tank 2 at the given rate of 2 gallons per minute. Solution also flows from Tank 2 into Tank 1 at the given rate of 1 gallon per minute. Solution drains out of Tank 2 at the given rate of 1 gallon per minute. Consider Q1 (t) = lbs of salt in Tank 1 at time t and Q2 (t) = lbs of salt in Tank 2 at give time t. Establish system of two differential equations, with initial conditions which explain amount of salt in the tanks. Express how long the system is valid for.