列位高人，在下近来做了几套面试模拟题，遇到一些不会的。列在了下面。希望如果有达人愿意帮助的话请把详细过程指导一下。万分感激！！！！

1.  Describe the method by which you would determine the relationship between the length of a spring and the stress under which it is under. Include details of how you would compute the precise relationship. What would you do as the spring approaches catastrophic failure?
请问这个是否该回答：P = dgh (d 位液体密度，g是重力加速度，常数，h就是那个井下深度)？那接下来的问题如何回答呢？

2. A stock has beta of 2.0 and stock specific daily volatility of 0.02. Suppose that yesterday's closing price was 100 and today the market goes up by 1%. What's the probability of today's closing price being at least 103?
彻底没概念啊。。。望达人指教


3. When cycling home at night, I notice that sometimes my rear light is switched off when I arrived home. Presumably the switch is loosse and can flip from on to off or back again when I go over bumps. I suppose that the number n of flippings per trip has a Poisson distribution e^(-lam)*lam^n/n!. If the probability that the light is still on when I arrive home is p, find lam.
望达人指教。。。

万分感激！！！！！