Consider a DMS with symbols s 1 , s 2 , and s 3 with probabilities 0.7, 0.15, and 0.15 respec- tively. (a) Calculate the source entropy. (b) Calculate the entropy of the second order extension. (c) Design a variable-length code, and provide the codeword statistics such as average codeword length, variance of the code, coding eciency. (d) In general, under what conditions the coding eciency can be 100%.