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A vat holds 20 cubic feet of liquid and is initially full. Watercontaining 6 grams of salt per cubic foot is being poured into thevat at the rate of 4 cubic feet per minute, and is instantly mixed.The mixed liquid is draining from the vat at 4 cubic feet perminute, so the vat is always full. Let y(t) denote the number ofgrams of salt in the vat after t minutes. Write the differentialequation for y(t) and use the graphical method to sketch twosubstantially-different solutions
