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Solution entering intop the tank contains 0.04 pounds of concentrate per gallon.

Therefore, lb.

From exercise 33,

gal, gal/min, .

From the result of exercise 31,

.

(a)

.

Substitute , and in the above expression.

.

Solution of first order linear differential equation is .

Where integrating factor .

Write the differential eqaution in the standard from .

Find integrating factor.

.

Find the constant by applying initial conditions.

.

Multiply each side by .

.

(b)

Find the time at which amount of concentrate .

.

Time is .

(c)

Find the quantity of concentrate in the solution as .

Consider .

Substitute in the above expression .

(a) .

(b) Time is .

(c)

Quantity of concentrate in the solution as , 

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