In O/N 2004 P6 Q1(ii) - I don't understand why we can't use (5P4/2!)*(5!/2!)
http://www.xtremepapers.com/papers/...AS Level/Mathematics (9709)/9709_w04_qp_6.pdf
http://www.xtremepapers.com/papers/...AS Level/Mathematics (9709)/9709_w04_qp_6.pdf