Eight hundred motor vehicle collisions occurred over 2 years

[Asclepius1]

Eight hundred motor vehicle collisions occurred over 2 years in a city with a population of 600,000; 600 of these accidents were alcohol related. During the same period, there were 400 fatalities due motor vehicle collisions, of which 75% were alcohol-related. Which of the following best represents the 1-year incidence of alcohol-related motor vehicle fatalities in this community?
A. Unable to determine from available information
B. 600 per 600,000
C. 450 per 600,000
D. 300 per 600,000
E. 150 per 600,000

----------------------------------------
I answered "A". But my ** performance on NBME is terrible low, sure that was a wrong answer. Actually my question is, can we calculate 1 year statistic value just divide 2-years value?
I mean 400*0.75 = 300 per 2 years => 150 per year.

[Asclepius1]

My answer is A. Unable to determine from available information . You gave me the incidence for 2 years and I don't think I can adjust it for 1 year.

[katya]

A. Unable to determine from available information

[AliShah]

Me too, A.