• The key is to notice that the men are placed according to their heights. If it were any other way the answer could not be deduced

Now, assign natural numbers in increasing order to each of the men, indicative of their heights.
Last man in row 1 is assigned 50, last one in row2 -100 and so on till last one in row 10-500
The last person in each row is the tallest one, A is the shortest in this set (50,100,150… 500), therefore  A is 50
Also the shortest in the last column, ie the set of(50,100,150… 500), is 50.
Since all other elements in the set containing shortest of each column, will ultimately contain elements from the first row (men in higher rows are taller),50 is the tallest of this set. Therefore B is 50