Please help , answer the question fully with each step

PROBLEM 2 A source has an alphabet fa, a, a, a,} with corresponding probabilities 10.1, 0.2, 0.3,0.4 1. Find the entropy of the source. 2. Design a Huffman code for this source and compare the average length of the Huffman code with the entropy of the source. 3. Design a Huffman code for the second extension of the source (take two letters at a time). What is the average codeword length? 4. Which one is the more efficient coding scheme