In source coding, that is, representing symbols coming from a source by binary sequences, the code is considered optimal if the expected codeword length is equal to the source entropy. In the following Table, a source is shown that generates just four symbols, together with the symbol probabilities, and codewords that represent them. Examine whether the code is optimal. Symbol Symbol Probability Codeword A 0.5 1 B 0.25 01 C 0.125 001 D 0.125 000