Good evening Professor:

here is the question I have problem with

A corporation maintains a manufacturing division that manufactures printed circuit boards and an assembly division that produces final products. Currently, the manufacturing division has sufficient capacity to manufacture an additional 5,000 circuit boards. An external market exists for circuit boards. The market price for one circuit board is $80 and the cost to sell is $10. The fixed manufacturing cost per circuit board is $15, and the unit variable cost is $50. The assembly division plans to purchase 4,500 circuit boards. Management of the assembly division thinks that it can purchase from the manufacturing division at a lower price since both divisions are under the common control of the corporation. What is the minimum transfer price between the manufacturing division and the assembly division?

*Source: Retired ICMA CMA Exam Questions.

My question is

1.the cost to sell is also variable cost , why it is not included in the minimum transfer price.

2.what is the contribution margin for one circuit boards it $20 (80-10-50) or $30(80-50)

3.does transfer price only consider variable manufacturing costs

thank you very much for your time!