求教cfa一级quantitative methods问题！！答案表示看不太懂呀（哭） quantitative methods, 定量分析, 一级

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1.A stock has an expected mean return of 8 percent and standard deviation of 2 percent. Assuming the return is normally distributed, the probability that the return will fall between 6 and 10 percent is closest to:
A.        50%
B.        68%
C.        90%
选b，过程是怎么出来的呢？答案只表明了和shortfall risk有关

2.At the beginning the stock price is $10. The price movement of the stock follows a one-period binomial process. The upside of the stock price is 1.06 times the original price, and the downside is 0.94 times the original price. If the average ending price after a 5000 independent is 10.2, what is the probability of an up move(p)?
A.        0.11
B.        0.66
C.        0.18
选b，考点是binomial distribution