Answer:
CF
Step-by-step explanation:
we know that
An <u><em>angle bisector</em></u> is a line that divide an angle into two equal angles.
In this problem
---> given problem
---> by addition angle postulate
so
CF is an angle bisector of angle 
So, the area of a circle is a=pi r^2
so do that and get a=pi(4)
and since the circle touches the edge of the rectangle, the rectangle is 4 cm tall, so 4*8 is 32 and pi(4) is about 12.56, so 32-12.56 is 19.44, and I believe that is the answer. (19.4)