Practice assessment 2 - Question 10 (rollover relief)

in Business Tax
Please can someone help with this question as I'm not sure how to get to the answer AAT provided:
In 2017, James made the following purchases of trading properties:
12 July 2017, a retail unit for £250,000
1 August 2017, a factory for £325,000
On 31 July 2018, James sold a warehouse unit for £350,000, realising a gain of £75,000.
James's rollover relief claim for the 2018/19 tax year is: £50,000.
How do you get to £50,000?
This is hurting my head
In 2017, James made the following purchases of trading properties:
12 July 2017, a retail unit for £250,000
1 August 2017, a factory for £325,000
On 31 July 2018, James sold a warehouse unit for £350,000, realising a gain of £75,000.
James's rollover relief claim for the 2018/19 tax year is: £50,000.
How do you get to £50,000?
This is hurting my head

Comments
"You may be able to delay paying Capital Gains Tax if you:
sell (or ‘dispose of’) some business assets
use all or part of the proceeds to buy new assets"
https://www.gov.uk/business-asset-rollover-relief
You're ignoring the retail unit because it's not like-to-like to warehouse, where Factory and warehouse are like-to-like.
You sold an asset for £325,000, you bought a new asset for £350,000, this means you lost (spent) £25,000 more.
£325,000 - £350,000 = £-25,000
Gain of Sale: £75,000
Minus the loss: -£25,000
Total rollover relief: £50,000 (£75,000 - £25,000)
Norvydas Valavicius.
Norvydas Valavicius.
The retail unit qualifies as a business asset but was purchased over a year before the warehouse disposal therefore out of time for the relief.
The proceeds (£350k) were not entirely reinvested within the qualifying period (only £325k was). The proceeds which were not reinvested (£25k) remain in charge.