Consider the grammar given below: $S \rightarrow Aa$ $A \rightarrow BD$ $B \rightarrow b \mid \epsilon$ $D \rightarrow d \mid \epsilon$ Let a, b, d, and be indexed as follows: Compute the FOLLOW set of the non-terminal B and write the index values for the symbols in the FOLLOW set in the descending order. (For example, if the FOLLOW set is {a, b, d, }, then the answer should be 3210) Answer: _______.

To compute $\text{FOLLOW}(B)$:

1. From the production $A \rightarrow BD$:

   $$\text{FOLLOW}(B) \text{ includes } (\text{FIRST}(D) \setminus \{\epsilon\})$$

   Since $D \rightarrow d \mid \epsilon$, $\text{FIRST}(D) = \{d, \epsilon\}$. Therefore, $d \in \text{FOLLOW}(B)$.

2. Since $\epsilon \in \text{FIRST}(D)$, $\text{FOLLOW}(B)$ also includes $\text{FOLLOW}(A)$:

   $$\text{FOLLOW}(B) \supseteq \text{FOLLOW}(A)$$

3. From the production $S \rightarrow Aa$:

   $$\text{FOLLOW}(A) = \{a\}$$

   Therefore, $a \in \text{FOLLOW}(B)$.

4. Thus, $\text{FOLLOW}(B) = \{a, d\}$.

5. Using the given indexing:

   • $a \rightarrow 3$

   • $d \rightarrow 1$

Arranging the indices in descending order gives 31.