Simplified CFG means:
1. Remove useless productions.
2. Remove epsilon productions.
3. Remove unit productions.
S->Aa. since A is useless.
After step 1, grammar would be:
S->B
B->a|bC
C->a|^
After step 2, grammar would be:
S->B
B->a|bC|b
C->a
After step 3, we will get:
S->a|bC|b
B->a|bC|b
C->a
Now, Production of B are useless (unreachable from S), so final CFG is
S-> a|bC|b
C->a
Therefore, total of 4 productions.