29. 
Here is a magic square using the numbers 1 to 16 (with no repeats) arranged so the magic total of the numbers along every row, column and diagonal is 34.
It is possible, by replacing ONLY ONE of the numbers and then rearranging all of them, to make the magic total 36.
To do that  which number must be replaced by what?

1  14 
15  4 
8  11 
10  5 
12  7 
6  9 
13  2 
3  16 
