A pond has been dug at the Indian Statistical Institute as an inverted truncated pyramid with a square base. The depth of the pond is 6 m. The square at the bottom has side length 2 m and the top square has side length 8 m. Water is filled in at a rate of $\frac { 19 } { 3 }$ cubic meters per hour. At what rate is the water level rising exactly 1 hour after the water started to fill the pond?