Maximum price

Dear Tutor, I have a question from the exam kit from Kaplan, Q: 66 P is considering whether to continue making a component or to buy it from an outside supplier. It uses 12,000 of the components each year. The internal manufacturing cost comprises: $/unit Direct materials 3.00 Direct labour 4.00 Variable overhead 1.00 Specific fixed cost 2.50 Other fixed costs 2.00 ––––– 12.50 ––––– If the direct labour were not used to manufacture the component, it would be used to increase the production of another item for which there is unlimited demand. This other item has a contribution of $10.00 per unit but requires $8.00 of labour per unit. What is the maximum price per component, at which buying is preferable to internal manufacture? A $8.00 B $10.50 C $12.50 D $15.50 The answer is D. There is a working for labour costs W1) Relevant cost = Contribution Forgone + Direct labour = $10/2 + $4 = $9. Could you please explain to me the meaning of $10/2? I hought that the contribution forgone would be 10-8. Kind regards