Check the picture below.
[tex]\textit{area of a circular ring}\\\\ A=\pi (R^2-r^2) ~~ \begin{cases} R=\stackrel{larger}{radius}\\ r=\stackrel{smaller}{radius}\\[-0.5em] \hrulefill\\ R=10.5\\ r=7 \end{cases}\implies \begin{array}{llll} A=\pi (10.5^2 - 7^2)\implies A=61.25\pi \\\\\\ A\approx 192.42~m^2 \end{array}[/tex]
