Using his TightWad$($R$)$ database, Stu's MileageMiser has developed a new GPS based service to certify drivers for insurance discounts. He tracks their speeds, locations, and braking activity and delivers reports to insurance companies. January $1,2009$ he had $5,900$ paying customers. Of that group, a year later, $3,200$ were still customers. He spent $$15,000$ on programs designed to keep current customers happy and $$34,100$ on marketing to acquire new customers. His total number of customers on January $1,2010$ was $7,000.$ His revenue per customer is $$37$ per year and variable costs before marketing per customer are $$7$ per year.

For current customers, what is annual average customer margin after deducting the average retention spending?