Bronze Cowntact Tracing 2020 US Open Problem 3

Hi everyone,

I was working on the problem above. I don’t understand how the the x value or the possible cows that can be patient zero is 1 in the sample case. I think x would be 2 because if K = 0, then 1 and 2 can both start infected and not spread the infection.

(i) Exactly one cow on his farm could have started out carrying the disease (we’ll call this cow “patient zero”).

Exactly one cow.

Oh so only one cow can start off infected. The minimum K would be 1, because cow 1 infects cow 2. Cow 1 is the only cow that can be patient zero because it needs to infect cow 2.