The £50,000 cap is only applicable to other income of £200,000 which means you can relieve against the entire amount of trading income(here it is £60,000).
So the maximum loss that can be carried back under s.64 loss relief claim is £60000 plus higher of:
•£50,000 and •25% of £200,000(other income after deducting any gross amount of personal pension contributions)
That is £110,000 (= £60,000 plus £50,000).
(Adjusted income means all income after deducting personal pension contributions. But keep in mind that trading income is not subject to £50,000 cap).