Answer:
( c+a, b)
Explanation:
The length of the horizontal line is c by taking points D and C
( c-0) =c
So the length of line AB must also be c if it is a parallelogram
Let the coordinate of B be (x,y)
(x-a) =c
x = c+a
The height of the parallelogram is b by taking the difference of the y coordinates from A and D
A -D = b-0 = b
This must be the same form B and C
y -0 = b
y = b
The coordinates of B is ( c+a, b)