Look at this problem in this way:
(a^n)/n! = (a/1)(a/2)........(a/a)......(a/k)....
these all the terms are in multiplication.
So, in denominator, it'll start from 1 and in b/w it'll be the time when denominator will be equal to a and then terms in deno starts increasing.
The number in denominator will approach to infinity.
and (a/n) where n is close to infinity is Zero.
So, the whole term multiplied by 0 becomes 0.
Hence, the ans is ZERO.