Hypothesis Tests · Superchallenge problem

Ten patients are split at random, 5 to a new treatment and 5 to control. Four treated patients recover and one control patient recovers. Assume $H_0$: the treatment has no effect, so the same 5 patients would have recovered regardless, and every split into groups was equally likely. Find the exact one-sided p-value: the probability that at least 4 of the 5 recoverers land in the treatment group. Give a fraction.