What is the ruling on agreeing to receive an estimated daily wage based on the number of working hours, the center's income, and the number of patients scanned, or a fixed monthly salary with a percentage of the total income after deducting an estimated amount for expenses?

Combining a fixed wage (salary) with a percentage of the profit is not permissible according to the Four Imams, except for a weak narration among the Hanbalis and some of the Tabi'in. This opinion is the most preponderant and cautious. However, according to the view that permits combining a wage with a percentage of the profit, estimating the profit approximately does not affect its permissibility, because minor and necessary gharar (uncertainty) is excused, as stated by An-Nawawi.