Explanation:

To solve this problem, first calculate the area of the triangular park using Heron's formula.

- Calculate the semi-perimeter (s):

- $s=\frac{35+53+66}{2}=77\text{m}$

- Apply Heron’s Formula:

- Area = $\sqrt{s(s-a)(s-b)(s-c)}$

- Area = $\sqrt{77(77-35)(77-53)(77-66)}$

- Area = $\sqrt{77\times 42\times 24\times 11}$

- Calculated Area ˜ 923.50 $m^2$

- Calculate cost of levelling the park:

- Cost = Area × Rate

- Cost = $923.50\times 9.25$

- Cost ˜ Rs8,547

- Correct Option:

- Option 2: Rs8,547