power of test random sample

Mary’s cat Baskin requires food with an expected meat content of 80%. From past experience it is known that the meat content in cat food has a normal distribution with standard deviation 5%. Mary buys a crate of cat food for her beloved boy. Baskin decides that he will take a random sample of 10 tins of food, and that he will reject the whole crate if the average meat content (for the sample) is less than 75%. Determine the power of Baskin’s test if the expected meat content is actually 77%.