You are trying to restriction-map a plasmid. An EcoRI digest gives you a 10 kb fragment, an XhoI digest gives you a 2 kb and an 8 kb fragment, and the double digest gives you fragments of 2, 3, and 5 kb. From these results, you deduce that the size of the plasmid is kb, the number of EcoRI sites is , the number of XhoI sites is , and that there is an EcoRI site within the kb XhoI fragment