Why does the class have a dashed line once and a normal line once?

I have a task which requires me to draw a UML diagram based on the description. I have received the solution (see the photo). However, I can't figure out the solution and have a few questions why the solution is the way it is. I have described these below.

Description:

The contract of a prepaid cell phone should be modelled and implemented. A basic contract has a contract number (of type int) and a balance (of type double), but no monthly charges. The contract number is not automatically generated, but is to be set as a parameter by the constructor as well as the initial balance. The balance has a getter and a setter. The following options can be added to a contract (if needed also several times):

• 100 MB of data (monthly charge 1.00 €)
• 50 SMS (monthly charge 0.50 €)
• 50 minutes (monthly charge 1.50 €)
• Double Transfer Rate (monthly charge 2.00 €) Implement this this requirement with the help of the decorator pattern. All contract elements should be able to understand the methods getCharges():double, getBalance():double and setBalance (double).

The method getCharges() should provide the monthly charge of a contract with all its options selected. The methods getBalance() and setBalance(…) should be passed through and access the basic contract.

Exercise:

• Draw an UML-Diagram with all the classes / interfaces and their relationships, fields and methods (no constructors needed).
• Also provide a client class which holds a contract.

Solution:

Solution

Question:

• Why does Option once have a dashed line and a normal line to Contract?
• Why are the Minutes not listed as a class like Data and SMS?
• Why does Phone and DoubleTransfer have no connection to the other classes?