Cheers for the help but I already knew what the multiple of X and X' was. What I want to know is the determinant of the two? Or do you simply find the determinant of the 3x3 matrix that results from multiplying them together? I was led to beleive that:
|X'X| = |X'| x |X|
and given that both X and X' are non square matrices how do you find their determianants?