Answer:2
Step-by-step explanation;
Eighteen tens < 21 × (5+5)
Hope this helps!
The volume of a rectangular prism is L * W * H.
We are looking for whole numbers that multiply to 28.
There are 10 possible molds.
L, W, H
-------------
28, 1, 1
1, 1, 28
14, 2, 1
1, 14, 2
1, 2, 14
7, 4, 1
4, 1, 7
7, 1, 4
7, 2, 2
2, 2, 7
8minutes-2minutes=6minutes
6×80 copies = 480 copies