Stock returns vary from year to year. The more variance a stock displays the greater the potential risk. These are the rates of return for a stock over the last five years. Calculate the variance of these investment returns: 10, 30, 15, 5, 20. Hint: The variance of a series of numbers is the sum of the squares of their differences from the mean (average) of the numbers divided by the number of items in the series.

Martha is one producer in the perfectly competitive jelly industry. last year, martha and all of her competitors found themselves earning economic profits. if there is free entry and exit, what do you expect to happen to the number of suppliers in the industry and the price of jelly? the number of suppliers will increase, and the price of jelly will fall. the number of suppliers will decrease, and the price of jelly will increase. the number of suppliers will increase, and the price of jelly will increase. the number of suppliers will decrease, and the price of jelly will fall.