Schistosomiasis is a parasitic infection that is spread when larval forms of the parasite penetrate the skin
during contact with infested water. You are working in a village of 205 people, where it is hypothesized that spread of schistosomiasis is occurring through contact with local well water. You find that 125 of the villagers use the suspected well, while the rest of the villagers do not use the well. After gathering urine samples, you find that 104 of the villagers who use the well are infected with schistosomiasis. Only 15 of the villagers who do not use the well are infected.
How to calculate relative risk?