Transfer pricing pm

Hello sir I am referring to question 284(CTD) part b of Kaplan revision kit. I am writing all relevant facts. Divisions: FD - transfering TM - buying Target RI calculated RI FD. 85000. 0 TM. 105000. 180000 No. Of units transferred- 15000 Transfer price- 66 Target must be completed for bonus equal to 5% of RI. and both manager want to receive required targets. Calculate TM- max TPrice FD-. min TPrice What they did I was completely unable to understand why they did in such way. Ans max 71 Min 71.67 If you have any other way to ans please refer to question. Thank you sir.