I would arrange longest dimension of brick along longest dimension of tub. similarly next longest. so, 8*4*2 along 60*30*18

8*7=56(7 is the maximum no of bricks i can place along length) 4*7=28(7 is max i can place along side 30) 2*9=18(9 along side 18) so, 7*7*9 bricks = atleast 441 bricks can be placed.

Also,we can divide the volume directly by that of cube ,that is, (60*30*18)/(4*2*8)=506.25. so, it may be possible to place a maximum of 506 bricks.

so, the correct answer would lie some where between these limits. i hope that makes sense.