Now the way the problem is asked, we're only getting one legitimate critical point here. So that's probably going to be the x at which we achieve a minimum value. But let's use our second derivative test just in case to make sure that we're definitely concave upwards over here, in which case that this will definitely be the x value at which we achieve a minimum value. So the second derivative of our cost function is just the derivative of this, which is going to be equal to 40 minus 180 times negative 2, which is negative 360. So it's going to be plus 360 over x to the third. The derivative of this is negative 2 times negative 180, which is positive 360, x to the negative 3 power, which is exactly this right over here. So when x is equal to 1.65, this is going to be positive.