In endurance horse racing, people over the age of 15 are called seniors and people 15 years or younger are called juniors. An endurance horse race consists of 25 seniors and 5 juniors. (Give answer as a fraction or a decimal out to at least 4 places. If your answer is very small use scientific notation for example 3.3421E-6.) What is the probability that the top three finishers were:

(a) all seniors

(b) all junior

(c) 2 seniors and 1 junior

(d) 1 senior and 2 juniors