Let $V$ be a binary code of length $n=9$ capable of detecting error patterns of two or fewer bits, but incapable of detecting all errors of three or more bits. If a code vector v in V is sent over a BSC $($Binary Symmetric Channel$)$ with transition probability $($i$.$e$.,$

with probability of error$)p=\frac{1}{10},$ then what is the probability $P_U$ of an undetectable

error? Please explain your answer. of an undetectable error? Please explain your answer.