P1.T4.202. Option pricing models (binomial)

Suzanne Evans

Well-Known Member
Questions:

202.1. Analyst Brian employs a recombining binomial tree to estimate the absolute value at risk of an asset ("absolute" signifies potential loss relative to the initial value). The initial value of the asset is $100.00. The horizon is 2.0 years and the tree has 8 steps; each time step in the tree is therefore three months (0.25 years). The real-world probability (p*) of an up movement is 44.0%. The up step size (u) = 1.20 and the down step size (d) = 1/u = 0.833.; both are per (0.25) step. Which is nearest to the two-year 99.0% absolute value at risk (VaR)?

a. $17.25
b. $33.18
c. $47.00
d. $66.51

202.2. Bob tries to value a three month European put option with a one-step binomial tree (one step = 0.25 years). The price of the non-dividend-paying stock is $100.00 and the put option is at-the-money (ATM) with a strike price of $100.00. The asset volatility is 36.0% per annum with continuous compounding. The riskless rate is 4.0%. Bob decides that volatility will inform the size of the up (u) and down (d) steps according to a Cox, Ross Rubinstein (CRR) model; i.e., if the number of steps were increases the asset price would tend toward a lognormal distribution.

a. $2.89
b. $8.43
c. $15.05
d. $20.76

202.3. Risk Manager Mark is pricing a six-month American put option on a non-dividend-paying stock when the stock price is $105.00. The put option is out of the money (OTM) as the strike price is $100.00. Mark assumes a two-step tree such that each step is three months. He assume a 6.0% riskless rate with continuous compounding. Instead of "matching volatility with up (u) and down (d) size movements," Mark simply assumes the size of the up movement is +20% and the size of the down movement is -20%; i.e., u = 1.20 and d = 0.80. What is nearest to the estimate of the price of the American put option? (variation on GARP 2012 Sample Questions 7 and 8)

a. $5.34
b. $6.80
c. $7.29
d. $8.51

Answers:
 

cash king

New Member
Anyone can help me with Q.202.1?

By my understanding, in binomial tree setup, given p* and u, the real-world annum expected return miu=-0.0221; sigma=0.3646.
Since binomial tree follows that ln(St)~norm(ln(S0)+(miu-signma^2/2)*dt, sigma*sqrt(dt))
then the 99% percentile of ln(St) is:
ln(S0)+(miu-signma^2/2)*dt-2.33*sigma*sqrt(dt)=3.227
the 99% percentile of St is: exp(3.227)=$25.20
then the anwer is VaR=100-25.19=$74.80

I wonder what is wrong in my calcuation?
 
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