In a survey of 100 people, S, D and C are the sets of people who like swimming, diving and cycling respectively. 10 people like all three activities. The number who like exactly two of the three activities is 3 times the number who like all three. 25 people like swimming only, 20 like diving only, 15 like cycling only, and the remaining people like none of the three activities.
(a)Find the number of people who like exactly two of the three activities.(1)
(b)Find the number of people who like none of the three activities.(2)
(c)Given that a randomly chosen person from the survey likes at least two of the activities, find the probability that they like all three.(3)
(Total for Question 17 is 6 marks)