math
posted by terry .
in a group of 100 people, 40 own a cat, 25 own a dog and 15 own a cat and a dog. Find the probability that a person chosen at random
a) owns a dog or a cat
b) owns a dog or a cat, but not both
c)owns a dog, given that he owns a cat
d) does not own a cat, given that he owns a dog.

A: 80/100
B: 65/100
C: 15/100
D: 25/100