While she was at the store, it purchased 871 dress shirts that were listed for $54 each less trade discounts of 21%, 6%, and 4% from FXFusion in Vancouver. The store's operating expenses are 27% of cost and markup is 66% of cost. The store sold 529 shirts at the regular selling price. During a sale, it offered a markdown of 10% and sold another 202 shirts. It sold another 140 shirts at the break- even price. What is the single equivalent rate of discount for the three discounts on the cost only? Answer must follow format of xx.xx rounded to 2 decimal places and include appropriate units. Answer: