As the graph you see below, we named the red part "RedField".The read
part is the intersection of an ellipse and a triangle.Now, 8600‘s not
good at math, so he wants you to help him calculate the area of the
"RedField".
The first line of input contains n, the number of test cases. n lines
follow.Each test case contains four numbers a, b, x, y(0 < b <= a
<= x),and a is the lenth of OA, b is the lenth of OB,and x, y
representing the coordinate of the point P.
For each test case, output the area of the "RedField",accurate up to 2 decimal places.
