大家帮忙看看这道题

zzh2011flyusa

The figure shows a large square formed by fitting three L-shaped  tiles and one small square tile together. If a rectangular floor 10 feet by  12 feet is to be tiled in large squares of this design, how many L-shaped  tiles will be needed?
(A) 810    (B) 405   (C) 270   (D) 135    (E) 45

        8inches
      8inches