Differentation (Business Calculus)

I can't really figure out what I need to plug in. Here is the problem ...

At 0 degrees Celsius, the heat loss H (in kilocalories per square meter per hour) from a person's body can be modeled by

$\displaystyle H=33(10*\sqrt{v}-v+10.45)$

Where v is the wind speed (in meters per second)

a.) Find $\displaystyle \frac{dH}{dv}$and interpret it's meaning in this situation

b.) Find the rates of change of H when v=2 and v=5

Thanks in advance. Word problems tend to confuse me