$A$ stone is dropped into a quiet lake and waves move in circles at a speed of $8 \,cm/sec$. At the instant when the radius of the circular wave is $12 \,cm$, how fast is the enclosed area increasing?
- A$180 \pi \,cm^2/sec$
- B$196 \pi \,cm^2/sec$
- C$192 \pi \,cm^2/sec$
- D$200 \pi \,cm^2/sec$
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