For part (2b), the expression E should be drawn using nested boxes as shown in figure 3.
Figure 3: Expression E, drawn as a set of nested boxes.
Again, you should use OOT drawing procedures to create your diagrams.
For both (2a) and (2b), it is up to you to decide the details of exactly how these diagrams should look. They should be neat and attractive. Pick colors for the boxes and lines. Do not worry about the problem of very large expressions that cannot easily be drawn on on the screen.