假设信源符号为{a,b,c,d}，这些符号出现的概率分别为{0.2，0.2，0.4，0.2}写出对信源符号bdadc进行算术编码和解码的过程。-Assumptions for the source symbols (a, b, c, d), the probability of emergence of these symbols were written on (0.2,0.2,0.4,0.2) bdadc source symbols for arithmetic coding and decoding process.