Finding the maximum value in a specific row of a matrix

I have this matrix:

M = [3 6 1 -2; 3 0 -2 -4; 8 -3 5 4; -2 -3 -2 5];

And I need to find the maximum value in row 4, and next I need to know the maximum value in columns 2 and 3. I know it seems simple but I can't remember and the help command is not being very helpful. Thanks!