Estimate a population, then qualify a plug-in tail probability

The distance between a pupil’s home and school is $x$ km. A random sample of 60 pupils gives $\sum x=33.6$ and $\sum x^2=22.79$. Calculate unbiased estimates of the population mean and variance.

Estimate the probability that the mean value of $x$, for this sample, will be less than 0.5. State any assumptions or approximations used.