Incidence and Prevalence

Out of a class of 30 students, 3 were ill with a certain viral infection at the start of October; one recovered October 15, the other two remained ill throughout the month.  6 more students became ill between October 1 and 5; one of these recovered October 22.  One additional student became ill October 25 and remained ill through the end of the month.
 
The incidence of this illness for October was: ___ _________ (Points : 1) The point prevalence of this illness for October 20 was:  __ ______