Assume you enter into 5 long futures contracts to buy July gold for $1,400 per ounce. A gold futures contract size is 100 troy ounces. The initial margin is $14,000 per contract and the maintenance margin is 75% of the initial margin. What change in the futures price of gold will lead to a margin call?
选项：

A:$35 drop
B:$70 drop
C:$175 drop
D:$350 drop