can someone explain to me how this works please?

4. Assume a stock has a normal distribution, an expected return of 9% and a standard deviation of 4%, the stock's return should fall between and 66% of the time Answer: 5% and 14% 5. Assume a stock has a normal distribution, an expected return of 2% and a standard deviation of 9%, the stock's return should fall between and 66% of the time Answer: -7% and 11% 6. Assume a stock has a normal distribution, an expected return of 8% and a standard deviation of 8%, the stocks return should fall between and 66% of the time Answer: 0% and 16%