Question 4
Peter is about to shade some cells in the $6\times6$ grid which is shown on the right. Any two cells that share a side must at most have one shaded cell. While on those un-shaded cells, Peter writes a number which is the total number of cells that shares a side with this cell that are shaded. Given that all the numbers written is at most 3, what is the maximum number of cells that Peter can shade? Fill the grid with one possible solution of shaded cells and filling number.
