Futures Margin Question - Easy investor, contract, receive, posting

prav_Cfa7

A silver futures contract requires the seller to deliver 5,000 Troy ounces of silver. An investor sells one July selver futures contract at a price of $8 per ounce, posting a $2,025 initial margin. If the required maintenance margin is $1,500, the price per ounce at which the investor woudl first receive a maintence margin call is closest to:

A. $5.92
B. $7.89
C. $8.11
D. $10.80

**The answer is C. $8.11.

Why is it $8.11?

I eliminated A and B immediately because he is shorting it, therefore the call price has to be above $8.

Then I thought I should use:

Trigger Price = P0 * (1 + Initial Margin %) / (1 + Maintenance Margin %)

When I did this, I kept getting $8.64. Anyone know how to get $8.11?