[tex]\textit{area of a circular disk}\\\\ A=\pi (R^2-r^2) ~~ \begin{cases} R=\stackrel{larger}{radius}\\ r=\stackrel{smaller}{radius}\\[-0.5em] \hrulefill\\ R=10.5\\ r=7.5 \end{cases}\implies \begin{array}{llll} A=\pi (10.5^2-7.5^2) \\\\\\ A=\pi (110.25-56.25) \\\\\\ A=54\pi \implies A\approx 170~m^2 \end{array}[/tex]
