A$9$Iris $($who is single$)$ starts a business on $6$ July $2023,$ preparing accounts to $5$ April. Her adjusted trading loss for the nine months to $5$ April $2024$ is $15,000.$ However, she is expecting a trading profit of approximately $55,000$ in the year to $5$ April $2025.$

Before starting her own business, Iris was in employment. Her employment income in recent years has been as follows

$2019-2037,630$

$2020-2122,660$

$2021-2226,150$

$2022-2335,830$

$2023-24($up to $5$ July $2023)23,260$

She has no other income in any year between $2019-20$ and $2023-24$ inclusive. She is not a Scottish taxpayer.

Required:

$($a$)$Assuming $($for the sake of simplicity$)$ that income tax rates, bands and allowances for all years are the same as those for $2023-24,$ calculate the effective percentage rate of tax relief that Iris would obtain if she claimed each of the following reliefs in relation to her trading loss:

$$relief against total income for the year of the loss, or

$$relief against total income for the previous year, or

$$early trade losses relief, or

$$carry$-$forward relief.

$($b$)$Advise Iris as to the best course of action in relation to her loss.