A tank contains $1000\text{L}$ of pure water. Brine that contains $0.02\text{kg}$ of salt per liter enters the tank at a rate of $5\text{L/min}.$ Also, brine that contains $0.08\text{kg}$ of salt per liter enters the tank at a rate of $10\text{L/min}.$ The solution is kept thoroughly mixed and drains from the tank at a rate of $15\text{L/min}.$ Answer the following questions.

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1. How much salt is in the tank after $t$ minutes?
Answer (in kilograms): $S(t) =$

2. How much salt is in the tank after $2$ hours?
Answer (in kilograms):

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