Three, (Full marks 12 points) At the foot of the mountain is a pond, the scene: a steady flow (i.e., the same amount of water flows into the pond from the river per unit time) continuously flows into the pond. The pond contains a certain depth of water. If one Type A water pump is used, it will take exactly 1 hour to pump out all the water in the pond; if two Type A water pumps are used, it will take exactly 20 minutes to pump out all the water in the pond. If three Type A water pumps are used simultaneously, how long will it take to pump out all the water in the pond exactly?
Three, let the amount of water flowing into the pond from the spring every minute be $x$ m$^{3}$, each water pump extracts $y$ m$^{3}$ of water per minute, and the pond originally contains $z$ m$^{3}$ of water. It takes $t$ minutes for three water pumps to drain the pond. According to the problem, we have
$$
\left\{\begin{array}{l}
60 y-60 x=z, \\
20 y+20 y-20 x=z, \\
3 t y-t x=z .
\end{array}\right.
$$

Solving this, we get $t=12$.