To determine the rate of change in fuel economy for 10 km/h intervals, we need to analyze the given function that models the relationship between the vehicle's speed and fuel economy. However, the equation you've provided appears a bit disorganized, and I need to clarify the functional form. Based on what is usually given in problems like this, let's assume the fuel economy $F(x)$ is modeled by the equation:

$F(x) = 520 - 0.005x^2 + 10.8x$

where $F(x)$ is the fuel economy in kilometers per liter and $x$ is the speed of the vehicle in kilometers per hour.

Step 1: Rate of