Hypothesis testing — practice question

The areas, $X\;\text{cm}^2$, of petals from one species of flower have mean $\mu\;\text{cm}^2$. It was previously established that $\mu = 8.9$. After a change in climate, a botanist states that the mean is not still $8.9$. The areas of a random sample of $200$ petals from this species are recorded, and the data are summarized by $\Sigma x = 1850$, $\Sigma x^2 = 17\,850$.