Reappointment (BPP 8.26)

Hello Sir, This may be a basic question, but I really can’t catch it where it comes from

QUESTION:

BPP 7a.26 The following question is taken from the January to June 2016 exam period.
An accountant is using the repeated distribution method to reapportion service department costs. The following table shows the work she has done so far. Figures that are yet to be calculated are shown as
“???”
-Production – Production – Service – Service
-department – department – department – department
-1 – 2 – X -Y
$ $ $ $

Apportioned and allocated
Production overheads: 60,000— 80,000— 20,000— 10,000
Service department X: 8,000—10,000— (–20,000)— 2,000
Service department Y: 7,200— 4,200— 600— (–12,000)
Service department X: ???— ???— (–600)—-0
Total production overhead: ???— ???— 0—0

What is the total production overhead for production department 1 after the remaining reapportionment of the overheads of service department X?
$74,600
$75,200
$75,440
$75,467

ANSWER: By examining the second row of figures in the table it is clear that service department X’s costs are reapportioned on a 40% , 50% , 10%. On the final reapportionment no overhead is reapportioned to service department Y, so the balance of overhead should be reapportioned 40/90 and 50/90. This results in the following total production overhead for production department 1. ($60,000 + $8,000 + $7,200) + 40/90 x $600 = $75,467

MY QUEST: I haven’t started yet, I lost because I don’t see where 40% , 50% , 10% comes from, could you please enlighten me?