4. A 1000 litrecontainmenttankcatches the outflowfrom aprocessing apparatus whichhas 800 litresof water with2 gof chemicalagentdissolved in it.  Additional supplycomesinto thetank at 3 litres/hr containing5 g/litreof the chemical agent. Thesolution leaves thecontainmenttank at 3 litres/hr. When the amountof chemical agentin the containment tankreaches 500 g, no moresupplyis allowed to enter the system. Instead,fresh water is inputintothe tank at 2 litres/hr; andat the same time,the outflow isincreased to 4 litres/hr.  How much chemical agentisheldin thecontainmenttankat any time t.Assume all liquids arewell-mixed.(10marks
