Sports Company sells a make of dirtbike for $16,800. This normal selling price covers the overhead cost of 15% and the normal net profit of 10% of cost. The dirtbikes are sold for a price that allows the company to offer a 20% discount while still maintaining its regular gross profit. At the start of winter, the bikes was marked down. This company had an operating profit of $2,500 per bike at the new regular selling price. What was the rate of markdown?