An analyst is studying a stock that is currently trading at $35. The analyst estimates that there is 33% probability that the stock will trade at $50 after one year, a 20% probability that the stock will trade at $42, and a 47% probability that the stock will trade at $20. What is the volatility of this stock return?
A
15%
B
26%
C
36%
D
39%
这道题可以用ln(y1/y2)来算收益么