In this exercise, classes are suggested via the typewriter font, although you are free

to come up with other meaningful class names. Prepare a class diagram for a graphical document

editor, that supports grouping, as follows:

Assume the document consists of several sheets.

Each sheet contains drawing objects, including text, geometrical objects and

groups.

A group is a set of drawing objects, possibly including other groups.

A group must contain at least two drawing objects.

A drawing object can be a direct member of at most one group. It's allowed to be a

member of zero groups.

Geometrical objects include circles, ellipses, rectangles, lines, and squares.

As you draw the class diagram, pay attention to the aggregation and composition associations. Re$-$

call that aggregation $(diamond)$ is a kind of association in which an aggregate object is made of constituent

parts that can live independent of the object. Composition $(diamond)$ is an aggregation $(diamond)$ that: $(1)$ be$-$

longs to only one assembly $-$ multiplicity should always be $1-$ and $(2)$ it has a coincident lifetime

with the assembly $-$ deletion of the assembly triggers the deletion of all constituent objects.