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A stone is dropped into a quiet lake and...

A stone is dropped into a quiet lake and waves in circles at the speed of 5 cm/s. At the instant when the radius of the circular wave is 8 cm, how fast is the enclosed area increasing?

A

`8x cm^(2)/s`

B

`80 pi cm^(2)/s`

C

`6pi cm^(2)/s`

D

`8/3 cm^(2)/s`

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The correct Answer is:
B
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