The volume of the box is given as:

where l is the length, w is width and h is the height. Plugging the values given we have that:

Now the volume of the dices are given by:

plugging the length given we have:

Now to find out how many dices fit in the box we divide the volume of the box by the volume of the dice, then we have:

Therefore we can fit 1920 dices in the box and the anwer is B.