Answer: B) Profit per shirt goes from $10 to $15
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Step-by-step explanation:
Focus on the two points (2,0) and (3,10). The slope of the line through these points is
m = (y2-y1)/(x2-x1)
m = (10-0)/(3-2)
m = 10
Meaning the profit per shirt for this line is $10 per shirt.
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Now move onto the other line. Focus on the points (9,40) and (11,70)
m = (y2-y1)/(x2-x1)
m = (70-40)/(11-9)
m = 15
The profit per shirt has gone up to $15 per shirt