A 50 kg skydiver falls through the air and reaches terminal velocity after some time. The drag force is a function of velocity given by:

$${ F }_{ drag }=-b{ v }^{ 2 }$$

...where the negative sign denotes that the drag force is opposite to the direction of the velocity.

What is the terminal velocity of the skydiver (assuming the drag constant $b$ is 0.2 kg/m)?