Explanation:

- Problem Understanding: The volume of the original disc should equal the volume of the new disc because the material is melted and reshaped without any loss.

- Original Disc Volume Calculation:

- Formula: $\text{Volume}=\pi \times {\text{radius}}^2\times \text{thickness}$

- Volume = $\pi \times {12}^2\times 4$

- New Disc Volume Calculation:

- Let $h$ be the thickness of the new disc.

- Volume = $\pi \times {16}^2\times h$

- Equation Setup:

- Set the two volumes equal to each other:

$\pi \times {12}^2\times 4=\pi \times {16}^2\times h$

- Solving for $h$:

- $h=\frac{{12}^2\times 4}{{16}^2}=\frac{576}{256}=2.25\text{ inches}$

- Correct Option:

- Answer: Option 2: 2.25

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