make a rib

Hello,everyone:
When I make a rib ,I meet the problem.This is my code£¬what's the problem with it?
TopoDS_Wire W2 = BRepBuilderAPI_MakeWire(BRepBuilderAPI_MakeEdge(gp_Pnt(-30.,-4.,45.),
gp_Pnt(-50.,-4.,15.)));
Handle(Geom_Plane) aplane2 = new Geom_Plane(0.,1.,0.,4.);
BRepFeat_MakeLinearForm aform2(res1, W2, aplane2, gp_Vec(0.,8.,0.), gp_Vec(0.,0.,0.),
1, Standard_True);
aform2.Perform(); // new in 2.0
TopoDS_Shape res2 = aform2.Shape();