Assess Alice’s claim about mean mass

Suppose the mass of a man in Singapore is assumed to be normally distributed with mean 75 kg and variance $80\ \mathrm{kg}^2$. 100 men are randomly selected from the population and their sample mean mass is 77.2 kg. Alice claims that the population mean mass is actually more than 75 kg. Conduct a hypothesis test at the 5% level of significance.