A ip in a bitstring is a pair of adjacent bits that are not equal. For example,

the bitstring 010011 has three ips: The rst two bits form a ip, the second and third bits

form a ip, and the fourth and fth bits form a ip.

Question 6: A flip in a bitstring is a pair of adjacent bits that are not equal. For example, the bitstring 010011 has three flips: The first two bits form a flip, the second and third bits form a flip, and the fourth and fifth bits form a flip. Determine the number of bitstrings of length 7 that have exactly 3 fips at the following positions: The second and third bits form a flip, the third and fourth bits form a flip, and the fifth and sixth bits form a flip. . Let n 2 and k be integers with 0 s kn 1. Determine the number of bitstrings of length n that have exactly k flips