To find the rate of change in the purchase price (which represents the slope of the linear graph), we can use the formula for the slope between two points \((x_1, y_1)\) and \((x_2, y_2)\):
\[ \text{slope} = \frac{y_2 - y_1}{x_2 - x_1} \]
In this case, we have the points \((3, 8.25)\) and \((6, 16.50)\). We can assign the values as follows:
- \(x_1 = 3\), \(y_1 = 8.25\)
- \(x_2 = 6\), \(y_2 = 16.50\)
Now we can plug these values into the slope formula:
\[ \text{slope} = \frac{16.50 - 8.25}{6 - 3} = \frac{8.25}{3} = 2.75 \]
Thus, the rate of change in the purchase price of broccoli is 2.75 dollars per pound.