In a pollution study of 1500 indian rivers the following data were reported 
520 rivers were polluted by sulphur compound 335 were polluted by phosphate and 425 were polluted by crude oil 100 were polluted by crude oil and sulphur compound 180 by sulphur compound and phosphates150 by phosphate and crude oil and 28 were polluted by all three how many rivers were( 1)polluted by crude oil only (2)not polluted at all (3)not polluted by sulphur compound(4) polluted by only two impurities