Is it permissible for an engineer to agree with a subcontractor to supply a fence at a price of 200 riyals per meter, while taking a percentage of the profit, knowing that the lowest price offered to the company is 300 riyals per meter, and the actual supply price is 100 riyals per meter?

If the work is carried out under assignment and authorization from the company, then it is not permissible to take a commission from the institution unless the company gives permission. However, if the work is done independently outside official working hours, then there is no harm in taking a commission from the institution for the referral.