The answer is: A. 20.3
The explanation is shown below:
1. By definition, the sum of the length of the strings (The length of the blue segment and the length of the red segment) is equal to the length of the major axis (The black segment).
2. Based on this, you can write the following expression, where
is the length of the blue segment:

3. Now, you must solve for
, as following:


4. Therefore, the answer is the option A.
In a circle, the number of radians is proportional to the relative length of the arc, in comparison to the radius. We have that if we denote by x the radians, the following proportionality holds, relating angles and lengths:

because the total of angles in radians is 2pi and the total circumference is 2pi times the radius. Hence, by solving for x we get: x=4/7=0.57 rad
We also have that the area is proportional to the angles. The total are is

. Hence, A=
4 3/8 I think that is correct.
(4a + 6b) x (2a - 2b)
the answer would be 8a2 + 4ab - 12b2