We have :
the legnth ; a
height ; b
depth : c
When we stack them only a will change.
A(a,b,c) = a*b*c
A1(a1 b1 c1 ) = 28 * 20 * 15 = 8.400
A2 (a2 b2 c2 ) = (1.5*x) * 19.3 * 14.2
x ; Equals the time you should stack them.
A2 (a2 b2 c2 ) = (1.5*17) * 19.3 * 14.2 = 6988,53
b and c is constant.
We look if we have these requirements.
b1 => b2
20 => 19,3
c1 => c2
15 => 14.2
If yes, then we have to look at a.
a1 => a2
a1 => 1.5*x
a1 => 1.5*17
28 => 25,5
So the statement is true and everything is fine.