What is Huffman Coding in DAA?

SOLVED: Repeat the previous exercise for the code words 0, 10, 101, 111. Data from the previous exercise: Fred says that he ran the Huffman coding algorithm for the four characters A, C, G, and T, and it gave him the code words 0, 10, 111, 110, respectively. Give examples of four frequencies for these characters that could have resulted in these code words or argue why these code words could not possibly have been output by the Huffman coding algorithm.