$\begin{array}{l}A B=8 \mathrm{~cm}, C D=6 \mathrm{~cm} \\ A C=10 \mathrm{~cm} \text { (Pythagoras' theorem) } \\ R=10 \pi=30\end{array}$
I3.2 In Figure $1, A B C D$ is an inscribed rectangle, $A B=(S-2) \mathrm{cm}$ and $A D=(S-4) \mathrm{cm}$. If the circumference of the circle is $R \mathrm{~cm}$, find the value of $R$. (Take $\pi=3$ )