3.3. Znayka cut out a semicircle from paper. Neznaika marked a point $M$ on the diameter $A B$ of this semicircle and cut off two semicircles from Znayka's semicircle with diameters $A M$ and $M B$. Find the area of the remaining figure if the length of the part of the chord lying inside it, passing through point $M$ perpendicular to $A B$, is $2 \sqrt{7}$. If necessary, round the answer to two decimal places.
Answer: 21.99 (exact value: $7 \pi$).