Stone dropped in a lake, circular wave spreading: rate the enclosed area grows

1. A.
   $180\pi\ \text{cm}^2/\text{sec}$
2. B.
   $196\pi\ \text{cm}^2/\text{sec}$
3. C.
   $192\pi\ \text{cm}^2/\text{sec}$
4. D.
   $200\pi\ \text{cm}^2/\text{sec}$

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1. A.
   $66{\text{ }cm}^{2}/$ second
2. B.
   $122{\text{ }cm}^{2}/$ second
3. C.
   $132{\text{ }cm}^{2}/$ second
4. D.
   $110{\text{ }cm}^{2}/$ second

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1. A.
   $50\pi$
2. B.
   $60\pi$
3. C.
   $25\pi$
4. D.
   $70\pi$

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