The reflexion of a point P with coordinates (x,y) over the line y=x is the point P' with coordinates (y,x). For example, the reflection point of a with coordinates (10,2) is a' with coordinates (2,10).
For this reason, the point c y reflect in C' with coordinates (4,6).
What I did was 6 divided by 100 and I got 0.06 times the the 500,000 and got 30,000 so your answer should be 30,000. Hope this helps and let me know if I'm wrong. have a great day!