Now it'll be pretty straightforward to take the derivative. So let's say that v prime of x, v prime of x is going to be equal to, I just have to use the power rule multiple times, so four times three is 12x to the three minus one power, 12x squared, minus 200 times x to the first power, which is just x, plus 600. And so now we just have to figure out when this is equal to zero. So we have to figure out when 12x squared minus 200x plus 600 is equal to zero. What x values gets my derivative to be equal to zero? When is my slope equal to zero? I could also look for critical points where the derivative is undefined, but this derivative is defined, especially throughout my domain of x that I care about, between zero and 10.