Hypothesis testing — practice question

The lengths, in centimetres, of worms from a particular species are normally distributed with mean $\mu$ and standard deviation $2.3$. A magazine article says that $\mu=12.7$. A scientist wants to check whether this claim is correct. He measures the lengths, $x$ cm, of a random sample of $50$ worms of this species and obtains $\Sigma x = 597.1$. He intends to perform a test, at the $1\%$ significance level, of whether the actual value of $\mu$ differs from $12.7$.