6, and that's probably being a more than a bit generous. Yes, Roger C. Carmel was very good in this, but frankly I never much cared for this episode... it was too cute by a half. The goofy music and slapstick antics in the second half of the episode lent a Three Stooges aura to the events. And as great a producer as Gene Coon was, when he was off Roddenberry's leash--like he was here--he often went way overboard on the comedy. This episode plays a bit like Hogan's Heroes in outer space to me... and I never cared much for Hogan's Heroes (outside of the great theme music played during the opening credits).
But as we see in the blasphemous thread, "Doomsday Machine not best of TOS," it doesn't take that much to entertain some.... (sigh)... There, I said it. Like Korby told Andrea, "Deal with it!"
JUST KIDDING. Well, maybe not.
On a more serious note, one of the most disappointing things about TOS is how the series failed to sustain the great stories and the momentum they generated from the last 5-10 episodes of season one through the first 5-10 episodes of season two. By the time this episode was shot, TOS had started its slow downward trend in quality that would rapidly pick up steam in season three.