The numbers 1,2,…49 are placed in a 7×7 array, and the sum of the numbers in each row and in each column is computed. Some of these 14 sums are odd while others are even. Let A denote the sum of all the odd sums and B the sum of all even sums. Is it possible that the numbers were placed in the array in such a way that A=B? combinatorics proposedcombinatorics