T be an arbitrary tree where each ver Let s that is not yet initialized. For this problem, you are to witt fiw field v.dat that already contains a numerical value e different DFS algorthes to process T DFS tree traversal defines, for each vertex u in T, two canceptual tine se tht eccur tr oe er entry time for v, which is when the DFS is called to begin processing to, and the postorde eit tine Any r each vertex v in T, two conceptual time-steps that occur for u the preorde is when the DFS exits the call to process v, and will never again touch u. So a vertex u is frst entered ere is a time when it is last exited, which is its postorder exit time. During e at its preorder entry time. And t the time between u s ftrst visit and last visit, the subtree rooted by u is being processed by the DFS Simply put, a vertex v goes through three phases 1) v has not yet been discovered by the DFS 21 y has been preorder visitied but not yet postorder exited: the subtree rooted by o is being explored, and 3) u has been postorder exited (or postorder processed) by the DFS r questions a. through e. below with little effort, please understand that the processing caused by the call DFS(v) starts u's second phase (its preorder visit), - And if u is a child of v, then the fime between o's preoder wisit and postorder exit includes some of phase 1 for w that have been preorder processed by the time the DFS preorder processes (first visits) r. This sum should include.dat u, all ofphase 2for u, and some of phase 3 Tor u a. Write a simple DFS that for each vertex v in T, writes in v.ans the sum of all w.dat valus for the