The shaded areas add to 2/5 of the area of the circle, which is given by
A = πr²
Then the shaded area is ...
(2/5)A = (2/5)π(10 in)²
shaded area = 40π in²
The interest is $453.60.
The total amount includes principal + interest. The principal was 630 and the total amount was 1083.60.
1083.60 - 630 = 453.60.
At simple interest it will be 939+939×6×0.08=$1389.72.
It is how close it's form is to that of a circle, there is a formula for it that can be easily searched