IBPS PO RRB PO Prelims 6 Aug 2023 Shift 1 Paper

A shopkeeper buys an item for Rs. 500 and sells it at 20% profit but one customer buys it from him at the selling price for 4 years at a simple rate of interest, which is 5% per annum. How much profit percentage is earned by a shopkeeper if interest is also considered as profit?