An investor opens a margin account by selling short $8,000 worth of securities. What is the margin call?

For an initial transaction in a short margin account, the investor has to deposit 50% of the amount shorted, or $2,000, whichever is more per Regulation T. Because the investor is shorting $8,000 of securities, the required deposit will be ($8,000 * 50%) = $4,000.