The correct answer is B (6.4%). The discount rate (DR) for a money market instrument is calculated as follows:

$DR = \left( \frac{365}{\text{Days}} \right) \times \left( \frac{\text{Interest Earned}}{\text{Face Value}} \right)$

Substituting the given values:

$DR = \left( \frac{365}{160} \right) \times \left( \frac{140,500}{5,000,000} \right) = 0.0641 \approx 6.4\%$

• Option A (6.2%) is incorrect because it mistakenly adds the interest earned to the redemption value in the denominator.
• Option C (6.6%) is incorrect as it represents the add-on rate (AOR), which uses the present value in the denominator instead of the face value.