Questions related to margin in CFA Level 1 are not very difficult. The following is an important table:

where P0 is the initial price or contract price, Im is the initial margin, and Mm is the maintenance margin.

To gain the points, you have to:

1. Memorize the equations
2. Understand that for margin for purchase/sale, margin is quoted in % while that of futures is quoted in absolute value
3. For long margin (including that of future margin), trigger price has to be less than the initial price. For short margin (including that of future margin), trigger price has to be more than the initial price. Use this to check the answer and help you memorize the equations.
4. For securities, if the price falls or rises above Mm, one only has to increase the deposit back to Mm level. However, for futures, one must increase the deposit back to Im level!

E.g.

A future contract is purchased to cover 1000 ounces of gold for $500k. Assume the initial margin is $50k, at what price will the buyer receive a margin call if the maintenance margin is 30k? How much has to be deposited if the gold price falls to $470/ounce?

P0 = 500k / 1000 = $500/ounce

Initial margin = $50k/1000 = $50/ounce

Maintenance margin = $30k/1000 = $30/ounce

Therefore, the trigger price is $500 - $(50-30) = $480

Since $470 < $480, so a margin call will be initiated. The owner has already lost $30 per/ounce, so he/she must re-deposit $30 x 1000 = $30k to bring the balance back to Im.