Answer : 4 states
Explanation :
the given regular expression is for the language "2nd symbol from the right is b"
in such cases where the kth symbol from the right is asked, the no. of states in the dfa will always be 2k as we got to calculate/ keep memory of all possible strings ending combinations (2k)
Thus in our question, all possible strings from the right will give the answer 22=4 states