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1. We will derive a two-state put option value in this problem. Data: ; (i.e. r=

ID: 2761948 • Letter: 1

Question

1. We will derive a two-state put option value in this problem. Data: ; (i.e. r=10%). T=1 year. The two possibilities for are 130 and 80.

a. Show that the range of is 50 while that of put option is 30 across the two states. What is the hedge ratio of the put?

b. Form a portfolio by shorting three shares of stock and writing five puts. What is the (nonrandom) pay-off to this portfolio? What is the present value of the portfolio?

c. Given that the stock currently is selling at 100, show that the value of the put must be 10.91.

Explanation / Answer

Solution:

a. Given that uS0 = 130, dS0 = 80

Pu = 0 and Pd = 30

Hedge ratio = (Pu – Pd)/ (uS0 – dS0)

Hedge ratio = (30 – 0)/ (130 – 80)

Hedge ratio = 30/50

Hedge ratio = 3/5

b.

Riskless portfolio

ST = 80

ST = 130

Buy 3 shares

240

390

Buy 5 puts

150

0

Total

390

390

                         Present value = $390/1.10

Present value = $354.545

c. Portfolio cost : 3S + 5P = 300 + 5P

Value of the portfolio = $354.545

300 + 5P = $354.545

5P = $54.545

P = $10.91

Hence, the value of the put must be $10.91

Riskless portfolio

ST = 80

ST = 130

Buy 3 shares

240

390

Buy 5 puts

150

0

Total

390

390