Consider the following UML diagram:

A$.$ If there are six authors, what is the minimum and maximum

number of books? What's the minimum and maximum number

of readers?

B$.$ If there are six readers, what's the minimum and maximum

number of books? What's the minimum and maximum number

of authors?

$**$Note from professor$**$ When considering those questions related to min or max, we must consider it from two sides. For example, the multiplicity on the author side is $1$ to $2,$ and on the book side is $1$ to $3.$ Since one reader needs $1$ to $3$ books, when there are $6$ readers, we need $6$ to $18$ books. On the other hand, one book can be read by $1$ to $2$ readers, so $3$ books are enough to serve $6$ readers, and we need $6$ books at most. Therefore, we merge those data; the min is $3,$ and the max is $18.$