Investors can _51_ money simply by loaning it. The money they loan is called capital. Security (担保) is an expensive item which the borrower mortgages (抵押) to the investor to show that he intends to _52_ the debt. The way investors make money on loans is to charge interest. Interest is money that _53_ pay to investors for the use of their money. Interest is usually a certain percentage of the capital. Investors sometimes _54 ten percent or more interest per year. The interest may be calculated daily， monthly， or yearly. The interest must be _55_ before the capital can be repaid. If the interest is not _56_ the agreed rate， the interest is added _57_ the capital. Then the borrower has _58_ pay interest on the unpaid interest _59_ on the capital. A debt can grow quickly this way. If the total of the capital and accumulated interest gets too high， the investor will take _60_ of the item used as security and sell it to get his money back.