Question 155
33 balls are placed on unit squares of a $10 \times 10$ board such that no unit square contains more than one ball. For each empty unit square we calculate the total number of balls located on the same row with this unit square and the total number of balls located on the same column with this unit square and after that the sum of these two numbers we write on this unit square. What is the maximal possible sum of all numbers written on the board?