Marnie conducted a survey of the cats in four shelters and wrote the following observations:
4 of the 18 cats in Shelter 1 were black
13 of the 24 cats in Shelter 2 were black
12 of the 20 cats in Shelter 3 were black
18 of the 25 cats in Shelter 4 were black

Based on the survey, which shelter had the greatest percentage of black cats?