Question

$ATC$ must fall simply because $AFC$ always falls. Comment.

Answer 1

No. $ATC=AFC+AVC$.

Being a component of ATCATC, falling AFCAFC implies falling ATCATC. But this is true only in the initial stages of production when average fixed cost is a significant component of ACAC. In the later stages of production, average fixed cost (because it is continuously falling) reduces to an insignificant component of ACAC. Accordingly, ACAC tends to rise along with the rising AVCAVC, even when AFCAFC tends to fall.