10-kb DNA fragment digested with restriction endonuclease EcoRI yielded fragments 4 kb and 6 kb in size. When digested with Bam HI, fragments 1, 3.5, and 5.5 kb were generated. Concomitant digestion with both EcoRI and BamHI yielded fragments 0.5, 1, 3 and 5.5 kb in size. Give a possible restriction map for the original fragment.