Logistic Model with Harvesting

If the growth of a population follows the logistic model but is subject to "harvesting" (such as hunting or fishing), the model becomes

where $\displaystyle h(t)$ is the rate of harvesting.

(a) Suppose that the harvest rate $\displaystyle h$ is constant. Determine the maximum sustainable harvest.

Hint: Set $\displaystyle y'=0$ and use the quadratic formula to find $\displaystyle h_{max}$

I've tried using the hint and setting the equation to 0 then using quad. form., but haven't had any luck on this. If any one could point me in the right direction on what to do, I'd really appreciate it.

What I have is:

$\displaystyle ry-ry^2/L-h=0$

$\displaystyle ry-ry^2/L=h$

But then it says to use for quadratic formula, so I'm not sure if I should be solving for h or what..