Answer:
Division N's purchase costs will decrease by $90,000 per year
Step-by-step explanation:
Division N's purchase cost form outside vendor = total units purchased per year x unit price = 30,000 units x $15 = $450,000
if Division N obtains the product form division M with a transfer price of $12 per unit, their costs will decrease by = total units x (vendor price - transfer price) = 30,000 units x ($15 - $12) = $90,000 per year