1.
Let A=[aij]A = [a_{ij}] be a 5×55 \times 5 matrix, where aij{0,1}a_{ij} \in \{0, 1\}, 1i,j51 \le i, j \le 5. The number of matrices AA such that the sum of elements of each row is 11 and the sum of elements of each column is 11 is: