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)
Explanation : S → iE tSS1\a
S' ⇒ eS|a
E → b
This is left factor grammar
Thus we may expand S to ibtSS' on input i and
wait untill ibtS has been seen to decide whether
to expand S' → eS|∈