here 6 permutations are possible as A corresponds to one of A',B',C'
and B corresponds to one of remaining A',B',C' and C corresponds to third of A',B',C'
therefore A lies on L1, B lies on the line of intersection of P1and P2 and C lies on L2 on the plane of P2
therefore A' lies on L2=C
B' lies on the line of intersection of P1and P2=B
C' lies on L1 on the plane of P1=A
i.e permutation of [A'B'C']=[ABC]