Changing a Dominant Strategy

Two competing retailers have profit payoffs (in tens of thousands of dollars) based on their pricing strategies, listed as (Retailer 1, Retailer 2): (8, 8) if both price high; (2, 10) if Retailer 1 prices high and Retailer 2 prices low; (10, 2) if Retailer 1 prices low and Retailer 2 prices high; and (5, 5) if both price low. What is the minimum rebate a supplier must offer to a firm for choosing the high-price strategy to make that strategy dominant?