Assume that Selling Division and Buying Division are both owned by Overall Corporation. Selling Division sells a product that is used by Buying Division and outside customers. Selling Division has 27,000 units of excess capacity. Selling Division currently sells the product for $90 per unit and Buying Division currently buys 27,000 units of the product from an outside source for $90 per unit. Variable costs of the product are $18, of which $4.5 is the cost of selling the product to an outside customer. Using Selling price less avoidable costs as the minimum price, fill in the following formula for the desired transfer price: $ x