Question: A cohort study is conducted to determine the relationship between visual impairment and the risk of injuries from falls among the elderly. A total of 400 visually impaired persons aged 70 or older are compared to 400 persons of comparable age without visual impairment. Over a 5-year follow-up period, 80 visually impaired persons have injuries from falls and 20 non-visually impaired persons have injuries from falls. Calculate the relative risk of falls among elderly visually impaired persons. (Show your work)