To determine which two points indicate a rate of change of 80 km per hour, we need to calculate the slope (rate of change) between pairs of points on the graph. The formula for the slope (rate of change) between two points \((x_1, y_1)\) and \((x_2, y_2)\) is:
\[ \text{slope} = \frac{y_2 - y_1}{x_2 - x_1} \]
In this case, we want the slope to equal 80 km/hr.
Let's analyze the provided points:
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Points (4, 320) and (6, 480): \[ \text{slope} = \frac{480 - 320}{6 - 4} = \frac{160}{2} = 80 \]
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Points (5, 400) and (6, 560): \[ \text{slope} = \frac{560 - 400}{6 - 5} = \frac{160}{1} = 160 \text{ (not 80)} \]
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Points (4, 480) and (6, 600): \[ \text{slope} = \frac{600 - 480}{6 - 4} = \frac{120}{2} = 60 \text{ (not 80)} \]
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Points (4, 400) and (6, 480): \[ \text{slope} = \frac{480 - 400}{6 - 4} = \frac{80}{2} = 40 \text{ (not 80)} \]
From the calculations, the only pair of points that indicates a rate of change of 80 km per hour is:
(4, 320) and (6, 480).