Treatment of property losses b/fwd at 06/04/2017

[FarmerJack]

Assume:
Landlord has property losses b/fwd at 06/04/2017 of £30,000.

2017/2018 Rents received (net of agents' costs) = £10,000
FC (finance charges) = £5,000

What is the loss carried forward at 05/04/2018?
Is it
A) £30,000 - (£10,000 - £5,000) = £25,000
or
B) £30,000 - £10,000 = £20,000 with unused tax reduction of 75% of £5,000 to be c/fwd to future years

Any comments would be extremely welcome.
Thank you in advance.

[maths]

If in 17/18 net rental income pre finance costs is 10,000 then profit is 10,000 less 75% of 5,000 i.e. 10,000 less 3,750 giving 6,250 to be further reduced by loss b/f of 30,000 i.e. loss available for c/f [30,000 less 6,250].

[FarmerJack]

Thank you, maths, for your answer.
This is very helpful indeed.
Best wishes.