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.