Under the hood memory management, w/o Garbage collection.

Hello all. Let us say that I have this (simplistic) code:
a=list( 1 2 3 4 5 6 7 8 )
a=car(a)
b=list(2 3 4)
The question is this: assuming that no "proper" garbage collection has been done. I.e., if the next command after b=list(1 2 3) will be gc(), memory footprint will change.
What happens is that a now takes far less space than it did in the past. Now b consumes more memory.
What will the SKILL engine do?

1. allocate more memory to contain variable b, and subsequent memory requiring
2. It will it use the memory release, after variable a needs less space, and garbage collection will simply relieve any excess memory?
My guess would be that  item 1 will happen.

Thanks.