Shoes and Shoes, Inc. supplies shoes to defense personnel. In the process of manufacturing shoes it also produces rubber mats which are also sold. In the month of May, 25,000 units of shoes were manufactured, which also resulted in production of 7,500 rubber mats. 20,000 shoes were sold during the month at a unit price of $10 and 6,000 rubber mats were sold at a unit price of $5. Joint costs incurred in this process amounted to $150,000. What is the gross margin of Shoes and Shoes for the month of May using the sales method