Compare the expected message length when an ASCII file is compressed by the following three methods.
Huffman-with-header. Read the whole file, find the empirical frequency of each symbol, construct a Huffman code for those frequencies, transmit the code by transmitting the lengths of the Huffman codewords, then transmit the file using the Huffman code. (The actual codewords don't need to be transmitted, since we can use a deterministic method for building the tree given the codelengths.)