The principle of shelf$-/$layer$-$based packing...

Select one or more:

$2.$

uses the widest unpacked item to determine the size of the layer

b$.$ uses the highest unpacked item to determine the height of the layer

C$.$ can be applied to $2-$D and $3-$D problems

d$.$ can be applied to $2-$D problems only

e$.$ leads to guillotine patterns in the $2-$D case