A binary source has symbol probabilities 0.8 and 0.2. If extension coding (blocks of 4 symbols) is used, the lower and upper bounds on the average code word length are :
(a)lower___________.
(b) higher_________.

An image uses $$512\, \times \,512$$ picture elements. Each of the picture elements can take any of the 8 distinguishable intersity levels. The maximum entropy in the above image will be

A source produces 4 symbols with probabilities $${1 \over 2},\,{1 \over 4},\,{1 \over 8}\,\,and\,\,{1 \over 8}.$$ For this source, a practical coding scheme has an average codeword lenght of 2 bits/symbols. The efficiency of the code is :