Question

Matias stacked his cubes to make this rectangular prism.

Answer 1

Answer:

The answer is 80

Answer 2

I FOUND YOUR COMPLETE QUESTION IN OTHER SOURCES.
 SEE ATTACHED IMAGE.
 The problem can be modeled as a pair of matrices:
 First matrix:
 (4) * (4) = 16
 Second matrix:
 (16) * (5) = 80
 Since the second matrix depends on the first, then the number of cubes is:
 N = 80
 Answer
 80 cubes.