Question 1060855
8000 people in town
5000 men *1/2=2500 who drink; 3000*(0.40)=1200 who drink.
The probability of (man OR drinks) is (50/80)+(37/80)-both (25/80)=62/80=31/40
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Number of people who drink are 2500 men and 1200 women or 3700 altogether. 
If the person is known to drink heavily (3700), the probability the person is a man is 2500/3700 or 25/37.