Correctly order the following steps of fracture repair, placing a 1 by the first step, a 2 by the second step, and so on.          

____Osteoblasts in the periosteum lay down a bone callus of primary bone.          

____Damaged blood vessels bleed and fill the gap between the bone fragments with a hematoma.          

____The bone callus is remodeled and replaced with secondary bone.          

____Fibroblasts, chondroblasts, and blood vessels enter the clot, and the soft callus begins to bridge the gap between bone fragments.