Going rate to do farm accounts and other small sole trader accounts

Susanf1

I do accounts for my brother who is a dairy farmer - putting all the income and expenses in a file and recording them and preparing and submitting his Form 11 returns. He has some miscellaneous dividends as well . I am a qualified accountant but not working directly in the field. I'm wondering what the going rate for this work would be at arms length. ? Same for small sole trader Form 11s with approx. 200 sales receipts and 200 expense items per annum? Thanks alot.