Consider the planes P1:2x+y+z+4=0P2:y−z+4=0 and P3:3x+2y+z+8=0 Let L1,L2,L3 be the lines of intersection of the planes P2 and P3, P3 and P1, and P1 and P2 respectively. Then,
(1) at least two of the lines L1,L2 and L3 are non-parallel
(2) at least two of the lines L1,L2 and L3 are parallel
(3) the three planes intersect in a line
(4) the three planes form a triangular prism