$2.$ AT$\backslash$&T needs a database in order to maintain track of its consumers, subscription plans, and mobile phones. The essential elements of importance to the operator, as well as their relationships, are depicted in the E$-$R diagram below. Answer the following questions using the illustration as a guide and explain your reasoning. Identify the element$($s$)$ in the E$-$R diagram that you utilized to determine your answer for each question. $(10$ pts$)$

For example:

Can prospective Manufactures that did not produce any Handset types be represented on this diagram?

Answer: Yes. Relationship between manufacturer and Handset Type are optional on Handset side. $($Or any other explanation in ER terms that supports your answer$)$ Questions: $($please type$/$insert your answers below$)$

$2\mathrm{.}1.$ Can a customer have an unlimited number of plans?

$2\mathrm{.}2.$ Can a customer exist without a plan?

$2\mathrm{.}3.$ Is it possible to create a plan without knowing who the customer is$?$

$2\mathrm{.}4.$ Does the operator want to limit the types of handsets that can be linked to a specific plan type?

$2\mathrm{.}5.$ Is it possible to maintain data regarding a handset without connecting it to a plan?

$2\mathrm{.}6.$ Can a handset be associated with multiple plans?

$2\mathrm{.}7.$ Assume a handset type exists that can utilize multiple operating systems. Could this situation be accommodated within the model included in the Figure?

$2\mathrm{.}8.$ Is the company able to track a manufacturer without maintaining information about its handsets?

$2\mathrm{.}9.$ There are two relationships between Customer and Plan. Explain how they differ.

$2\mathrm{.}10.$ Characterize the degree and the cardinalities of the relationship that connects Customer to itself. Explain its meaning.