Answer: 20%

### Explanation The maintenance margin requirement is calculated as the equity per share divided by the current price per share. Here’s the breakdown: 1. **Initial Equity**: 30% of $50 = $15. 2. **Actual Price**: $43.75 (the price at which the margin call occurs). 3. **Equity at Margin Call**: Initial equity + (Actual price - Initial price) = $15 + ($43.75 - $50) = $15 - $6.25 = $8.75. 4. **Maintenance Margin Requirement**: Equity at margin call / Actual price = $8.75 / $43.75 = 20%. - **Option A (13%)**: Incorrect. This option mistakenly uses the relative change in stock price as the margin requirement: ($50 - $43.75) / $50 = 12.5% ≈ 13%. - **Option B (18%)**: Incorrect. This option divides by the initial price instead of the actual price: ($15 + $43.75 - $50) / $50 = $8.75 / $50 = 17.5% ≈ 18%. - **Option C (20%)**: Correct. It accurately reflects the maintenance margin requirement as equity per share divided by the current price per share.

Author: LeetQuiz Editorial Team