Of 2,872 persons who had received radiation treatment in childhood because of an enlarged thymus, 24 persons developed thyroid cancer and 52 persons developed a benign thyroid tumor during follow-up period. a comparison group consisted of 5,055 children who had received no such treatment (brothers and sisters of the children who had received radiation treatment). during the follow-up period, none of the comparison group developed thyroid cancer, but 6 persons developed benign thyroid tumors. calculate the relative risk for benign thyroid tumors: and interpret your result. (1.5 point for calculation and 0.5 for interpretation. show details of your calculation)