A futures contract is written on 100 ounces of gold. The initial margin per futures contract is $2500. The maintenance margin is 75% of initial margin. An investor has a short position in 6 futures contracts. Her margin account balance is $12800 on day 0. The futures price on day 0 is $676 per ounce. The futures price on day 1 changes to $687. explain what happens to the margin balance on day 1. Is there a margin call and if so, what is the size of the margin call?