4. (a) Because traffic is growing heavy in the central part of a city, traffic engineers are planning to change all the streets, which are currently two-way, into one-way streets. Explain how to model this problem. (9 marks) Build a binary search tree for the words Dublin, Galway, Kildare, Kerry, Kilkenny, Mayo, and Wicklow using alphabetical order (b) (16 marks) (c) Show that pre-order traversals of the ordered rooted trees displayed in Figure 6 produce the same list of vertices. Figure 6 (8 marks)