img = new 
Array("img/index_r4_c2b.gif","img/index_r4_c3b.gif","img/ndex_r4_c4b.gif","img/ndex_r4_c5b.gif","img/ndex_r4_c6b.gif","img/ndex_r4_c7b.gif");
bfImg = new Array();
for(i=0; i<img.length; i++) {
  bfImg[i] = new Image();
  bfImg[i].src = img[i];
}