Pre-Dec 2023 Mock Exam. Section B. Contract with customers

Hello!

So i have searched everywhere for this answer and can not find it. Hence my question.

In the section B of the Pre-Dec Mock exams, Nationa Co had a contract with a customer. Details below:

Nationa Co. entered into a contract on 01st Feb. ’15 for 10 bikes.
Total price of contract= £150000

Usual charge by Nationa Co. for both packages:
Price per bike=£15000
Price per bike (maintenance)= £3750.

calculate Nationa Co’s revenue to be recognized for the year ended 30th June ’15

Now, to get the standalone price, i did a percentage thus:

Total price received= £150000
Total price usually charged=£187500.(£3750*10+£15000*10)
150000/187500*150000=£120000
(37500/187500*150000)*5/12=£12500. (5 months Feb-June).

And i got a total of £132500(£120000+£12500). But the answer given as the correct one was: £142500. I have absolutely no idea how they came about this figure. Please help!. Thank you very much.