On April 13, a stereo store received a new sound system with a list price of $2500 from the manufacturer. The stereo store received a trade discount of 25%. The invoice, with terms 2/10, n/30, arrived on the same day as the sound system. The owner of the store marked up the sound system by 60% of the invoice amount (before cash discount) to cover overhead and profits. The owner paid the invoice on April 20. How much extra profit will be made on the sale, as a percent of the regular selling price, due to the early payment of the invoice?