$A$ circular disc of radius $3 \text{ cm}$ is being heated. Due to expansion,its radius increases at the rate of $0.05 \text{ cm/s}$. Find the rate at which its area is increasing when the radius is $3.2 \text{ cm}$.

  • A
    $0.320\pi \text{ cm}^2\text{/s}$
  • B
    $0.300\pi \text{ cm}^2\text{/s}$
  • C
    $0.350\pi \text{ cm}^2\text{/s}$
  • D
    $0.400\pi \text{ cm}^2\text{/s}$

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