Interest Rate Parity Black Scholes 4888C3
1. **Problem Statement:**
(a)(i) Compute the forward rate premium of the Tanzania Shilling (Tsh) with respect to the Kenyan Shilling (Ksh) using Interest Rate Parity (IRP).
(a)(ii) Compute the six-month forward exchange rate given the spot rate and interest rates.
Demonstrate IRP applicability for a Kenyan investor with 1,000,000 Ksh.
(b) Compute the value of a European call option on Kakuzi Ltd shares using the Black-Scholes model.
2. **Formulas and Rules:**
- Interest Rate Parity forward premium formula:
$$\text{Forward Premium} = \frac{(1 + i_{domestic} \times t)}{(1 + i_{foreign} \times t)} - 1$$
where $i$ is the annual interest rate and $t$ is the fraction of the year (0.5 for 6 months).
- Forward exchange rate:
$$F = S \times \frac{(1 + i_{domestic} \times t)}{(1 + i_{foreign} \times t)}$$
where $S$ is the spot rate.
- Black-Scholes call option price:
$$C = S_0 N(d_1) - K e^{-rT} N(d_2)$$
where
$$d_1 = \frac{\ln(\frac{S_0}{K}) + (r + \frac{\sigma^2}{2})T}{\sigma \sqrt{T}}$$
$$d_2 = d_1 - \sigma \sqrt{T}$$
$N(\cdot)$ is the cumulative standard normal distribution, $S_0$ is current stock price, $K$ strike price, $r$ risk-free rate, $\sigma$ volatility, $T$ time to maturity in years.
3. **Calculations:**
(a)(i) Forward rate premium:
- $i_{Tsh} = 0.2025$ per annum
- $i_{Ksh} = 0.1775$ per annum
- $t = 0.5$
$$\text{Forward Premium} = \frac{1 + 0.2025 \times 0.5}{1 + 0.1775 \times 0.5} - 1 = \frac{1 + 0.10125}{1 + 0.08875} - 1 = \frac{1.10125}{1.08875} - 1 = 1.0113 - 1 = 0.0113$$
So, the forward premium is approximately 1.13%.
(a)(ii) Forward exchange rate:
- Spot rate $S = 0.12$
$$F = 0.12 \times \frac{1.10125}{1.08875} = 0.12 \times 1.0113 = 0.12136$$
So, the six-month forward exchange rate is approximately 0.12136 Ksh per Tsh.
(a)(iii) Applicability of IRP for Kenyan investor with 1,000,000 Ksh:
- Invest in Kenya at $i_{Ksh}$:
$$\text{Amount after 6 months} = 1,000,000 \times (1 + 0.1775 \times 0.5) = 1,000,000 \times 1.08875 = 1,088,750$$
- Convert to Tsh at spot rate:
$$1,000,000 \times \frac{1}{0.12} = 8,333,333.33 \text{ Tsh}$$
- Invest in Tanzania at $i_{Tsh}$:
$$8,333,333.33 \times (1 + 0.2025 \times 0.5) = 8,333,333.33 \times 1.10125 = 9,177,083.33 \text{ Tsh}$$
- Convert back to Ksh at forward rate:
$$\frac{9,177,083.33}{0.12136} = 75,635,135.14 \text{ Ksh}$$
This large number suggests a miscalculation in currency conversion; correct approach is:
- Convert initial Ksh to Tsh:
$$1,000,000 \times \frac{1}{0.12} = 8,333,333.33 \text{ Tsh}$$
- Invest in Tanzania:
$$8,333,333.33 \times 1.10125 = 9,177,083.33 \text{ Tsh}$$
- Convert back to Ksh at forward rate:
$$9,177,083.33 \times 0.12136 = 1,113,750 \text{ Ksh}$$
Compare with Kenyan investment:
- Kenyan investment after 6 months: 1,088,750 Ksh
- Investing in Tanzania and converting back yields 1,113,750 Ksh
Difference due to forward premium confirms IRP applicability.
(b) Black-Scholes option pricing:
- $S_0 = 4.50$
- $K = 3.50$
- $r = 0.10$
- $\sigma = 0.40$
- $T = 0.25$ (3 months)
Calculate $d_1$:
$$d_1 = \frac{\ln(\frac{4.50}{3.50}) + (0.10 + \frac{0.40^2}{2}) \times 0.25}{0.40 \times \sqrt{0.25}} = \frac{\ln(1.2857) + (0.10 + 0.08) \times 0.25}{0.40 \times 0.5} = \frac{0.2513 + 0.045}{0.20} = \frac{0.2963}{0.20} = 1.4815$$
Calculate $d_2$:
$$d_2 = 1.4815 - 0.40 \times 0.5 = 1.4815 - 0.20 = 1.2815$$
Using standard normal distribution values:
- $N(d_1) \approx 0.9307$
- $N(d_2) \approx 0.8997$
Calculate call price:
$$C = 4.50 \times 0.9307 - 3.50 \times e^{-0.10 \times 0.25} \times 0.8997 = 4.188 - 3.50 \times 0.9753 \times 0.8997 = 4.188 - 3.07 = 1.118$$
So, the current value of the call option is approximately 1.12.
**Final answers:**
- Forward premium: 1.13%
- Six-month forward rate: 0.12136 Ksh/Tsh
- Kenyan investor gains by investing in Tanzania and converting back, confirming IRP.
- Call option value: 1.12