Explanation:

- The area of the square with a side $s$ is 625 cm². So, $s\times s=625$. Solving, we find $s=25$ cm.

- The radius $r$ of the circle is 1/5 of the side of the square. Thus, $r=\frac{25}{5}=5$ cm.

- The breadth $b$ of the rectangle is 4/5 of the radius of the circle. So, $b=\frac{4}{5}\times 5=4$ cm.

- The length $l$ of the rectangle is given as 20 cm.

- Area $A$ of the rectangle is $l\times b=20\times 4=80$ cm².

The correct option is 4: 80.