Exercise 2.70: The following eight-symbol
alphabet with associated relative frequencies was designed to efficiently
encode the lyrics of 1950s rock songs.  (Note that the “symbols” of an
“alphabet” need not be individual letters.)


A    2    NA  16
BOOM 1    SHA  3
GET  2    YIP  9
JOB  2    WAH  1


Use generate-huffman-tree (Exercise 2.69) to generate a
corresponding Huffman tree, and use encode (Exercise 2.68) to
encode the following message:


Get a job
Sha na na na na na na na na

Get a job
Sha na na na na na na na na

Wah yip yip yip yip 
yip yip yip yip yip
Sha boom


How many bits are required for the encoding?  What is the smallest number of
bits that would be needed to encode this song if we used a fixed-length code
for the eight-symbol alphabet?