Answer (a) — incorrect: We should not combine cases from the Amoy Apartment Complex with cases from the Star Hospital because Star Hospital was the secondary wave of transmission. Combining all cases together will cause us to overestimate the incubation period.

Answer (b) — correct: By plotting the cases from the Amoy Apartment Complex and Star Hospital separately we can see that this is not a point source outbreak, but rather primary and secondary outbreaks of a person-to-person transmission outbreak.