The answer would be <span> inch, foot, yard, and mile</span>.
To do this, find the slope, y-intercept, and your goal.
Your goal is 500.
Your slope is 6.25 per orange.
Your y-intercept is 0 (you don't start out with anything.)
So, the inequality is

.
It is obvious that the radicals with negative sign tends to be less than those that are positive. So from there you already know a basic order. Now to be sure, you can use a calculator or just solve by squaring the whole number to find the radical form.
I think the answer is 10, 20, and 4