Option Valuation - CA Final SFM

Binomial Model
Formula
Remarks
VOC = P x Cu + (1 – P) x Cd
                           R
Where,
R = 1 + Rf
Cu = Call Upside Gain
Cd =  Call Downside Gain
Pu = Put Upside Gain
Pd =  Put Downside Gain
d = ds  (expected downside price divided by spot price)
       s
u = us  (expected upside price divided by spot price)
       s
VOC = P x Pu + (1 – P) x Pd
                           R
P = R – d
       U – d
Value of American Option  =  Max of Discounted Value or Intrinsic Value


Put Call Parity Theory (PCPT)

Spot Price + Value of Put = Value of Call + Present Value of Exercise/Strike Price

PCPT is the relationship between European Call and Put Option on the same stock, the maturity period and EP is same.
The PCPT equation is made to prevent arbitrage profit. If LHS ≠ RHS, then there would arise arbitrage profit.

LHS Þ SP + VOP    (Protective Put – S+, P+)
RHS Þ VOC + PV of EP   (Fiduciary Call – C+, ZCB+)

Risk Neutral Valuation
The Price of an option is independent of the risk preference of Investor Called risk-neutral valuation.

Black Scholes Model

Formula
Remarks
European Call Option = SP x N (d1) – PV of EP x N (d2)
Where,
Ln = Natural Log
SP = Spot Price
EP = Exercise Price
R= Rate of Interest
T = time 
d1 = ln (SP) + (r + .5 σ2) x t
              EP………………..
                        σt               
d2 = d1 -  σt               
Assumption of Block Scholes Model
European options are considered.
No Transaction Costs.
Short Term interest rates are known and constant.
Stocks don’t pay dividend.
Stock Price Movement is similar to random walk.
Stock returns are normally distributed over a period of time.
Variance of return is constant over the life of an option. 
    

When Probability distribution or probable market price is given for market price of share on expiration then value of option will be calculated as follows: -

Value of Option = (AMP –EP) x Probability + (AMP – EP) x Probability + ……………….. (.i.e. we should check individually)


Future/(1 + Rf) = Spot Price + PV of Storage – PV of Convince Yield

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