A local restaurant prides itself in having a high number of return customers. To build loyalty, the owner of the restaurant offers a free Prime Rib dinner (value $20) to any customer who purchases a meal during 10 previous visits. Meals purchased are tracked by stamps on a Loyalty Card. At the end of a month, the owner decides to calculate the customer retention cost. The data is the following: Number of Customers at Start of Month = 100 Number of Customers at End of Month = 120 Number of New Customers = 40 Value of Free Dinners Redeemed = $240 What was the Customer Retention Cost?