The quadrilateral ABCD is to be reflected across the line y = x, as shown in the diagram, to give a new quadrilateral, A'B'C'D'
B
A
7
6
5
4
3
4
-2
-3
-4
-8-7-6-5-4-3-2-1 1 2 3 4 5 6 7 8
-5
-6
D
-7
y=x
What are the coordinates of A?