Master Shoe Ltd. manufactures only one type of shoe and has two divisions, the Leather Division, and the Assembly Division. Both are 'profit centres'. The Leather Division manufactures soles for the Assembly Division, which completes the shoe and sells it to retailers. The Leather Division "sells" soles to the Assembly Division. It can sell all its production to outside customers as well, if it wants to. The market price for the Assembly Division to purchase a pair of soles from an outside supplier of soles is $15. (Ignore changes in inventory.) Both divisions can sell all its production to outside customers if required. Leather can currently sell all its production for $19 to outside customers .

Leather's costs per pair of soles are: Direct materials $4 Direct labour $3 Variable overhead $2 Division fixed costs $1

Assembly's costs per completed pair of shoes are: Direct materials $6 Direct labour $2 Variable overhead $1 Division fixed costs $7

Assume that Leather Division would save $1 in variable costs if their product was transferred to Assembly. What is the minimum transfer price per unit Soles should charge the Assembly division?