The rate of change of the area of a circle with respect to its radius $r$ at $r = 6 \text{ cm}$ is

  • A
    $10 \pi \text{ cm}^2/\text{cm}$
  • B
    $12 \pi \text{ cm}^2/\text{cm}$
  • C
    $8 \pi \text{ cm}^2/\text{cm}$
  • D
    $11 \pi \text{ cm}^2/\text{cm}$

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