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(a_{1} b_{1} c_{1} ) = 28 * 20 * 15 = 8.400

A2 (a_{2} b_{2} c_{2} ) = (1.5*x) * 19.3 * 14.2

x ; Equals the time you should stack them.

A2 (a_{2} b_{2} c_{2} ) = (1.5*17) * 19.3 * 14.2 = 6988,53

b and c is constant.

We look if we have these requirements.

b_{1 }=> b_{2}

20 => 19,3

c_{1 }=> c_{2}

15 => 14.2

If yes, then we have to look at a.

a_{1 }=> a_{2 }

a_{1 }=> 1.5*x

And since

a_{1 }=> 1.5*17

28 => 25,5

So the statement is true and everything is fine.