replace a portion of a matrix

I have a matrix. I need to replace value 1 with 5 of row 3 from column 2 to 4. and I need to replace value 1 with 5 of column 5 from row 2 to 4.

I =

     1     1     1     1     1     0     0     0     0     0
     1     1     1     1     1     0     0     0     0     0
     1     1     1     1     1     0     0     0     0     0
     1     1     1     1     1     0     0     0     0     0
     1     1     1     1     1     0     0     0     0     0

How to do this easily?Thanks in advance.

Answer 1

[Paulo Silva]

I(3,2:4)=5;
I(2:4,5)=5;