Question: 2015 Winter Final - 3

Author: Michiel Smid

How many bitstrings of length 77 start with 1111 or end with 0000?

(a)

$2^{74} - 2^{69}$

(b)

$2^{73} + 2^{73}$

(c)

$2^{77} - 2^{69}$

(d)

$2^{77} - 2^{73} - 2^{73}$