Final answer:
The slope of the graph represents the cost per ounce of coffee, indicating that for every extra ounce Lena buys, the cost goes up by approximately $2.99.
Step-by-step explanation:
When Lena graphs the relationship between the number of ounces of coffee (x) and the total cost (y), the slope of the graph represents the rate of change of the total cost with respect to the number of ounces. In this scenario, she pays $8.96 for every 3 ounces of coffee. To find the slope, which is the cost per ounce, we divide the total cost by the number of ounces, resulting in $8.96/3 = $2.9867 per ounce. The slope tells us that for every additional ounce of coffee Lena buys, the cost will increase by approximately $2.99.