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9 is the constan trate of change.

Step-by-step explanation:

Assuming two points of the graph with the form as P=(x,y) you can find the constant rate m using the slope formula.  

m=(y2-y1)/(x2-x1)

Lets say that P1=(0,0) and P2=(1,9), then:  

m= (9 – 0)/(1-0)

m=9

Therefore, the point (0,0) means that when you are not buying any t-shirt then you dont have any waste of money. The point (1,9) means that when you are buying one t-shirt then you have to pay 9 then its result that cost of each t-shirt is 9 so when you are buying two t-shirt then you  have to pay 18, when you are buying three you have to pay 27 likewise.

the clues that signal the reader should change tone are the punctuation marks, the grammatical signs. for example, the quotation marks at the beginning of something someone else said literally or the exclamation marks.

the tone of the first line of dialogue until "gettysburg" is a kind tone, a tone of advise. the narrator is trying to the other person in doing something he or she obviously is finding hard to do by giving a piece of advise and bringing up a memory of a successful similar case.

the clue that the reader understand how to read the word "bang" is the exclamation mark. it gives the word a surprise tone, a strong accent.

the best tone for reading the word "bang" is an exciting tone, a surprise one, even a loud one.

the words that should be read with a formal tone are the ones that give factual information. the sentence: mister lincoln couldn't think of anything to say at the gettysburg" gives information about an event and it needs to be read formally, also, when the narrator wants to transmit calmness, a formal and slow tone is needed, because people also transmit messages with the vibrations of our voices and tones.