We saw that there are 2N possible electron states in the 3s band of Na, where N

Question:

We saw that there are 2N possible electron states in the 3s band of Na, where N is the total number of atoms. How many possible electron states are there in the
(a) 2s band
(b) 2p band and
(c) 3p band?
(d) State a general formula for the total number of possible states in any given electron band.