Transfer Pricing Internally between Divisions

So i am having a struggle with this exercise.
The company XYZ have two divisions, the Division A and the Division B.
Division B monthly purchase 10.000 units to Division A, using as PTI total cost plus
5%. It is also known that the fixed costs incurred corresponding to 33% of total cost.
However, the Division A modernized its production equipment and wants to increase
the PTI to 18 euros/units.
The manager of Division B argues that it cannot support the new value as this would
lower their results to close to zero. Alternatively, the Division B can buy to an external
supplier for 16,5 euros/ unit., benefiting in this case a 45-day payment (cost of capital
opportunity is 4% / quarter). The Division A has no alternative use for this material.
Request:
Setting a price range for this transaction.