Study the following data and answer the questions.

"In a study of 1500 rivers the following data were reported: 520 rivers were polluted by sulphur compounds, 335 were polluted by phosphates, 425 were polluted by crude oil, 100 were polluted by both crude oil and sulphur compounds; 180 were polluted by both sulphur compounds and phosphates; 150 were polluted by both phosphates and crude oil and 28 were polluted by sulphur compounds, phosphates and crude oil."