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- Trees. The external path lengthof a binary tree is the sum of the lengths (number of ares) of the pasus from the root to all the leaves of the tree. 1. What is the external path length of the following tree? 2. A regular binary treeis a binary tree where every internal node has exactly twa subtrees. Write a recursive function that computes the external path length of a regular binary tree, assuming that you have at your disposal a Boolean function that tells you whether a tree is a leat and an inteent function that returns the number of leaves of a binary tree. int EPL (treeType t)... 3. Show the trace of execution of the function defined in (b) on the tree given in (a). EPL(A)=