Null and Alternative Hypothesis

A vending machine that dispenses coffee into cups must fill the cups with 7.8oz of liquid. Before selling the vending machine to a college or business, the company tests the machine to be sure it is dispensing an average amount of 7.8oz of coffee.  A sample of 20 amounts is shown below. The amount of coffee dispensed is assumed to be normally distributed with a standard deviation of 0.05 oz.
Ounces dispensed
7.78 7.79
7.82 7.82
7.87 7.84
7.80 7.82
7.80 7.78
7.83 7.75
7.85 7.83
7.84 7.73
7.82 7.87
7.81 7.88