An investor invested $$500$ two years ago at $7$ percent interest. The first year, the investor earned $$35$ in interest, which they left in the account. The second year, the investor earned $$37\mathrm{.}45$ in interest. The extra $$2\mathrm{.}45$ they earned in interest the second year is referred to as:

Multiple Choice

simple interest.

bonus income.

free interest.

present value interest.

interest on interest.