4. Consider the following AoN project network: (the first number above the node is activity duration, second number is resource requirement), Suppose the resource available is 10 . Assume that you are using the branch and bound procedure to solve this resource-constrained project scheduling problem, a) At what time instant occurs the first resource conflict? b) Give the minimal delaying alternatives that can solve this resource conflict. c) Draw the branch-and-bound search tree of this level, using the critical path method determine the lower bound for each node in the tree. (You only need to draw the first two levels of the search tree, i.e. the root node and the second level nodes, which solve the first resource conflict)