Question 121
Find the smallest integer $b$ with the following property: For each way of colouring exactly $b$ squares of an $8 \times 8$ chessboard green, one can place 7 bishops on 7 green squares so that no two bishops attack each other.
Remark. Two bishops attack each other if they are on the same diagonal.
Remark. Two bishops attack each other if they are on the same diagonal.