Investigators enrolled 100 diabetics without eye disease in a cohort (follow-up) study. The results of the first 3 years were as follows:

Year 1: 0 cases of eye disease detected; 8 lost to follow-up

Year 2: 2 new cases of eye disease detected; 2 deaths; 10 lost to follow-up

Year 3: 3 new cases of eye disease detected; 2 more deaths; 13 more lost to follow-up.

Assuming that all events occurred at the end of each year, the incidence rate is calculated as:

a)5 / 100

b)5 / 63

c)5 / 270

d)5 / 250