code: public double[] TileBounds( int tx, int ty, int zoom ) {
          double[] min = PixelsToMeters(tx * tileSize, ty * tileSize, zoom);
          double minx = min[0], miny = min[1];
          double[] max = PixelsToMeters((tx + 1) * tileSize, (ty + 1) * tileSize, zoom);
          double maxx = max[0], maxy = max[1];
          return new double[]{minx, miny, maxx, maxy};
      }
docs: Returns bounds of the given tile in EPSG:900913 coordinates
  
  @param tx
  @param ty
  @param zoom
  @return the array of [w, s, e, n]