Ana smith,a psychology professor ,was planning a study of viewer responses to certain aspects of the movies Casablanca,High Noon, and vertigo. Upon surveying the class of 55 students, she determined the following data: 17 had seen Casablanca 17 had seen high noon 23 had seen vertigo 6 had seen Casablanca and High Noon 8 had seen Casablanca and vertigo 10 had seen High Noon and vertigo 2 had seen all the three of the movies How many students had seen a) exactly two of these movies b) none of these movies c) exactly one of these movies d) Casablanca but neither of other two