Under certain geographic conditions, the wind velocity v at a height x centimeters above the ground is given by v = K ln(x/x₀), where K is a positive constant (depending on the air density, average wind velocity, and the like) and x₀ is a roughness parameter (depending on the roughness of the vegetation on the ground). Suppose that x₀ = .7 centimeter (a value that applies to lawn grass 3 centimeters high) and K = 300 centimeters per second.

(a) At what height above the ground is the wind velocity zero?

(b) At what height is the wind velocity 1200 centimeters per second?