In class, you discover that out of 25 students, 2 of your classmates are at home

sick with a flu. What is the prevalence of influenza in your class?

a) 8.0%

b) 9.5%

c) 10.0%

d) 12.5%

Two weeks later, those two students have recovered (and are now immune to the virus - they cannot catch it again). Unfortunately another five people have come down with the flu. Remembering that the original two cannot catch the flu again, what is the incidence of influenza over the last two weeks?

a) 28.0%

b) 20.0%

c) 21.7%

d) 30.0%