Complete Question
The complete question is shown on the first uploaded image
Answer:
The correct option is B
Explanation:
The number of alphabet is n= 4 (a , b , c , d )
Generally the total number of string of length 10 over the 4 alphabets is
[tex]N = 4^{10}[/tex]
Gnerally the number of string of length 10 that does not include b is
[tex]T = 3^{10}[/tex]
Generally the number of strings of length 10 over the 4 alphabets that have at least one alphabet b somewhere in the string is
[tex]G = N - T[/tex]
=> [tex]G = 4^{10} - 3^{10}[/tex]
