A silver futures contract requires the seller to deliver 5,000 troy ounces of silver. An investor sells one April silver futures contract at a price of $15 per ounce, posting an $8,400 initial margin. If the required maintenance margin is $6,900, the price per ounce at which the investor would first receive a maintenance margin call is closest to:

a) $16.38

b) $14.70

c) $13.62

d) $15.30