Problem 3. Networking in English Letters and bits

Alice transfers information in English alphabets to Bob. There are 26 distinct alphabet letters; only alphabets are treated and capitalization is ignored. Part a uses the letters so that they are equally frequent while Parts d-f use the letters for English language.

b. Alice transforms each letter to bits and transfer the corresponding bits to Bob for each letter. Assuming that Alice cannot send a fraction of bits and she wants to be efficient (the less number of bits the better), how many bits are needed per letter?