Hypothesis Testing - finding the power and beta!

A medicine dispensing machine is designed to discharge on average at least 8ml of medicine per dose with a standard deviation of 0.2ml. The amount of medicine per dose is normally distributed.

a) If you select a random sample of 16 doses and you are willing to have an (alpha or significance level)=0.02 risk of committing a Type I error, compute the power of the test and the probability of a Type II error (beta) if the population mean amount dispensed is actually 7.9ml per dose.

The answers are:
power = 0.4785 (+/- 5%) Beta= 0.5215 (+/- 5%)

I've been trying to figure it out using the formulas from the book but am having trouble. Please help!