I think the quantities on both sides are equal. What do you think.
Since the point is reflected about the y=x line, the coordinates are flipped. So, a=d and b=c. Looking at (a,b), we can see that b>a and for (c,d), c>d. Quantity A is a+d which are both small and Quantity B is b+c which are both greater hence the addition of both the points irrespective of the value will be greater than a+d. The answer is B.