Hypothesis Tests · Superchallenge problem

A one-sample $t$ test of $H_0$: $\mu = \mu_0$ with $n = 9$ has $\bar x - \mu_0 = 4$ and a two-sided $p$-value of exactly $0.05$. Find the sample standard deviation $s$ ($t^* = 2.306$ for $8$ df). Give your answer to the nearest hundredth.