Problem Solving

All of the stocks on the over-the-counter market are designated by either a 4-letter code or 5-letter code that is created by using the 26 letters of
the alphabet. which of the following gives the maximum number of different stocks that can be designated with these codes?
a) 2(26^5)
b) 26(26^4)
c) 27(26^4)
d) 26(26^5)
e) 27(26^5)

For 4 digit code , since no codition mentioned for repetition,

26^4

For 5 digit code,
26 ^5

Since it is "OR"

26^4+26^5 = 26^4(1+26)
= 26^4(27)

answer : 27(26^4)