Consider a daily stock trading window from June 6 to December 2, 2022. The three EV charging station companies had made different stock returns, where Blink made a 0.026% average daily return, Charge  Point made -0.054% and Plug Power made 0.011%. Meanwhile, their stock returns had different risks measured by standard deviation, where Blink made 5.052%, Charge Point made 5.469%, and Plug Power made 5.416%. Is there any way to lower the risk by using these three companies’ stocks? If so, then how? Provide an investment strategy based on statistics and portfolio investment theory.