can yoh explain why the correct answer is B

Alfred Thompson, a stock trader, buys stock on margin at $30 per share at a leverage ratio of 2. Due to the high volatility of the instrument, the maintenance margin requirement for the position is 40%. Given that the trader has purchased 200 shares, determine the share price below which he will first receive a margin call. OPTION A: $21.0. OPTION B: $25.0. OPTION C: $27.5