Suppose a type of glass is such that, for any incoming light: 70 percent of light shining from one side is transmitted through to the other side; 20 percent of the light is reflected (off of the outer surface) back in the direction from which it came; the remaining 10 percent is absorbed in the glass.

How much of an original light source will be transmitted through three panes of glass? It is assumed that the panes are parallel and at a small distance from each other.

Ignore any loss of light above or below the panes (which is the same as assuming the panes extend infinitely in all four directions). Express your answer as a ratio of integers.