Answer:
The volume of existing cage = length x widht x height = 3 x 2 x 3 = 18 cubic ft
Now she wants cage with volume four times of this cage
New Volume = V1 = 18 x 4 = 72 cubic ft
Keeping length same = 3 ft
Length x width x height = V1
3 x Width x height = 72
Width x height = 72 /3
Width x height = 24
Now multiple of 24 must be the width and height.
Taking width = 6 ft and height = 4 ft, we will get our answer
Proof:
Length x width x height = V1
3 x 6 x 4 = 72