Rhino viruses typically cause common colds. In a test of the effectiveness of echinacea, 42 of the 48 subjects treated with echinacea developed rhinovirus infections. In a placebo group, 77 of the 94 subjects developed rhinovirus infections. What is the percentage of subjects treated with echinacea who developed rhinovirus infections?
1) 35.42%
2) 87.23%
3) 52.08%
4) 81.91%