 
 <translate> 3-letter codes = 26^3;
4-letter codes = 26^4;
5-letter codes = 26^5;
Total = 26^3 + 26^4 + 26^5 = 26^3(1+26) + 26^5 = 26^3*27 + 26^5. The final answer: (D). <ibo> Koodu mkpụrụedemede 3 = 26^3; Koodu mkpụrụedemede anọ = 26^4; Koodu mkpụrụedemede ise = 26^5; Ngụkọta = 26 ^ 3 + 26 ^ 4 + 26 ^ 5 = 26 ^ 3 (n'ihi na 1 + 26) + 26 ^ 5 = 26 ^ 3 * 27 + 26 ^ 5. Azịza ya bụ: (D). 