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(a) \ \

The tank contains  of brine with  of salt per liter of water.

Pure water enters the tank at a rate of .

Brine contains of salt per liter of water.

Pure water enters the tank at a rate of .

Change in salt concentration of salt is the salt coming into the tank minus the salt going out of the tank. \ \

Salt coming into the tank is . \ \

. \ \

Salt going out of the tank is . \ \

Change in salt concentration of salt is .

Apply integral on each side.

\ \

\ \

.

The initial concentration of salt is , where .

\ \

.

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Substitute in .

Apply exponent on each side.

\ \

Therefore,the concentration of salt after minutes is  . \ \

(b)

Find the concentration of salt after one hour. \ \

Hence, .

Substitute in .

.

Therefore, the concentration of salt after one hour is .

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(a) The concentration of salt after minutes is  . \ \

(b) The concentration of salt after one hour is .