Mandolin Company has two divisions. Division A is interested in purchasing 10,000 units from Division B. Division B has enough excess capacity to produce these units. The per-unit market price is $30 per unit, with a variable cost of $18 and fixed cost of $5 at Division B. The manager of Division A has offered to purchase the units at $15 per unit. In an effort to make this transfer price beneficial for the company as a whole, what is the range of prices that should be used during negotiations between the two divisions