Red & Black Tree Insertion. (a) There is a red & black tree in Fig. 1. The value on each node is its key value. The color of each node can be inferred by its color and shape (rectangles represent black nodes and circles represent red nodes). Now you need to insert a node with key value 15, and draw the resulting red & black tree. (b) For the red & black tree in Fig. 1, insert a node with key value 7, and draw the resulting red & black tree. Note that your insertion should base on Fig. 1, not the resulting tree that you have for the previous