If I bought $10,000 worth of stock by putting up 60 percent of the selling price and borrowing the rest, how much have I borrowed? If the stock falls to $3,000 and a margin call is put in for the...

If I bought $10,000 worth of stock by putting up 60 percent of the selling price and borrowing the rest, how much have I borrowed? If the stock falls to $3,000 and a margin call is put in for the difference between the value of the stock and the amount I have borrowed, how much will I have to put up?