12 - 9. [Maximum mark: 10] On a school excursion, 100 students visited an amusement park. The amusement park's main attractions are rollercoasters (R), water slides (W), and virtual reality rides (V). The students were asked which main attractions they visited. The results are shown in the Venn diagram. R 32 12 10 18 V (a) A total of 74 students visited the rollercoasters or the water slides. Find the value of a. [2 (b) Find the value of b. [2 (c) Find the number of students who visited at least two types of main attraction. [2 (d) Write down the value of n( R n W). (e) Find the probability that a randomly selected student visited the rollercoasters. [2 (f) Find the probability that a randomly selected student visited the virtual reality rides