Suppose you deposit ​$600 in a bank account with a simple interest rate of 2.5​%. You want to keep your deposit in the bank long enough to earn at least ​$120 in interest. How long should you keep your deposit in the​ bank? To earn at least ​$120 ​interest, you should keep your deposit in the bank for blank ​year(s). ​(Round up to the nearest​ year.)