For figure 3:

Step 1:

The function is $\"\"$

Rate of change of a function is derivative of the function i.e $\"\"$ .

$\"\"$

Differentiating on each side with respect to $\"\"$ .

$\"\"$

Recall the formulae $\"\"$

$\"\"$

Step 2:

Rate of change of function at $\"\"$ is $\"\"$ .

Substitute $\"\"$ in $\"\"$ .

$\"\"$

$\"\"$ .

Solution:

$\"\"$ miles.