A is nullable, that is, A has a production which is epsilon.
Given that A is nullable, you have to revisit any productions containing one or more instances of A and replace them with the set of productions formed from every possible replacement of A with null, including no instances replaced and with all instances replaced.
So looking at the production S->Aa we need to replace it with the production where A is not replaced (the same production) and the production where A is replaced with null (which is s->a). Now there's three total productions for S.
When we look at the production A-> Ac we have to do the same thing, so Ac is replaced with Ac/c and we get...
You could rearrange it as necessary.
Sd does NOT become replaced with Sd/d because S is not nullable. There is no way to produce epsilon from S, so we don't replace S in productions.