In a book named Treasure, the reader has to figure out where a 2.2 pound, 24kt gold

Question:

In a book named Treasure, the reader has to figure out where a 2.2 pound, 24kt gold horse has been buried. If the horse is found, a prize of $25,000 a year for 20 years is provided. The actual cost of the publisher to purchase an annuity to pay for the prize is $210,000. What interest rate (to the nearest percent) was used to determine the amount of the annuity? (Assume end-of-year payments)

Annuity
An annuity is a series of equal payment made at equal intervals during a period of time. In other words annuity is a contract between insurer and insurance company in which insurer make a lump-sum payment or a series of payment and, in return,...