Every year, the veterinary hospital at a major research university treats a number of horses that have stones called enteroliths in their guts. A sample of 20 years shows that on average about 2% of horses presenting at the veterinary hospital are treated for enteroliths. Some breeds of horses seem more prone to developing enteroliths than others. Below is a table with the distribution of enteroliths among the breeds. Breed Arabian Thoroughbred Appaloosa Morgan Quarter horse Probability 0.3 .2 .15 .10 ? The probability that a horse arriving at the veterinary hospital is not an Arabian or a quarter horse is: (a) 0.55. (b) 0.25. (c) 0.45. (d) 0.75.