In an effort to determine the amount of food a male yellow-billed magpie eats in a day, a sample of $5$ birds from pet stores was observed. The birds ate the following amount of food: $60, 60, 50, 40,$ and $50$ grams. Find the mean and standard deviation weight of food in this sample. Do the computations step by step, without using the “standard deviation” function on your calculator, as in problem 9-52.