A rectangle is inscribed between the $x$-axis and the parabola $y=36-x^2$ with one side along the $x$-axis, as shown in the figure below. Let $x$ denote the $x$-coordinate of the point highlighted in the figure. Write the area $A$ of the rectangle as a function of $x$.

Please directly answer the question and provide the final value, e.g., 1, 2.5, 300.
Question: A rectangle is inscribed between the $x$-axis and the parabola $y=36-x^2$ with one side along the $x$-axis, as shown in the figure below. Let $x$ denote the $x$-coordinate of the point highlighted in the figure. Write the area $A$ of the rectangle as a function of $x$.

Please first conduct reasoning, and then answer the question and provide the final value, e.g., 1, 2.5, 300, at the end.
Question: A rectangle is inscribed between the $x$-axis and the parabola $y=36-x^2$ with one side along the $x$-axis, as shown in the figure below. Let $x$ denote the $x$-coordinate of the point highlighted in the figure. Write the area $A$ of the rectangle as a function of $x$.
