4. Your new job requires you to calculate the material costs for manufactured goods. One of goods you manufacture is a fabric sample in the shape of a circle. Given the formula $A=\pi r^{2}$, find the area $(A)$ of the fabric sample whose radius $(r)$ is $6.3 \times 10^{-8} \mathrm{~mm}$. Write your answer in scientific notation. (Use 3.14 for $\pi$ ) $A=$ $\sqrt{x} \mathrm{~mm}^{2}$

Step 1 ：Given the radius of the fabric sample is \(6.3 \times 10^{-8} \mathrm{mm}\) and we are asked to use \(3.14\) for \(\pi\).

Step 2 ：Substitute these values into the formula for the area of a circle, which is \(A=\pi r^{2}\).

Step 3 ：Calculate the area to get \(A = 1.2462659999999999 \times 10^{-14}\).

Step 4 ：Simplify the final answer to get \(A = 1.25 \times 10^{-14} \mathrm{mm}^{2}\).

Step 5 ：Final Answer: The area of the fabric sample is \(\boxed{1.25 \times 10^{-14} \mathrm{mm}^{2}}\).