 <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). <yor> Awọn koodu lẹta mẹta = 26^3; Awọn koodu lẹta mẹrin = 26^4; Awọn koodu lẹta 5 = 26 ^ 5; Apapọ = 26^3 + 26^4 + 26^5 = 26^3 ((1+26) + 26^5 = 26^3*27 + 26^5. Ìdáhùn tó péye: (D). 