I think answer shold be B(51,50)
you can take first small size for understanding
suppose i took (4,8) rectangle that ends at (3,2).
(1,1) – – – – – – (1,8)
…..so on
so on …..it's end at (3,2).
For(2,4), ends at (2,1)
For(3,6) ends at (2,5)
For(4,8) ends at (3,2)
For(5,10) ,ends at (3,8)
For(6,12) ends at (4,3).
For(7,14) rectangle ends at (4,11)
For (8,16) ...ends at (5,4)
We can get some idea that,
For Even number of rows, column increases 1 by previous column.
For Odd number of rows, difference of the present column and the previous even number column we get that particular column.
For row, the value repeats two times from row 2.
In this problem, (100, 200) i.e.
Even number row,
So column value must be 50 for 200 columns and row value must be 51 for 100 rows.
For even number of rows and columns,
Condition: Column =2*Row
(R, C) = {((Row/2) +1), Column/4} (this is generalize formula for this type of question).